It has been found that air pollution was a social problem since the beginning of the 14thcentury.Throughout the history,the United States and Britain made initial efforts to adopt laws and the air pollution control legislation.At the beginning of the 20th century,the industrialized countries set standard values for sulfur dioxide,particulate matter,carbon monoxide,oxidizing agents,nitrogen oxide,etc.Recently,the air pollution influence of regional area was obviously observed inUlaanbaatar,Mongolia.The most toxic pollutant of atmospheric pollution is fine particulate matter.To reduce the growing tendency towards premature death,cancer,respiratory diseases and asthma,the government tried to maintain and control the concentration of fine particulate matter in 2018.In addition,the scope of air pollution is expanding and people’s interest is increasing.In Mongolia,forty official air-monitoring stations started to collect the main pollutant concentration of air quality since 1996.The air monitoring stations were developed and tested new techniques to collected more accurate information of air ingredients such as ozone,carbon monoxide,nitrogen dioxide,fine particulate matter,and coarse particulate matter in 2008.In March,2017,the Mongolian Government authorized a National Program on minimization of atmosphere and surrounding contamination to regulate the usage of unimproved coal anywhere.Air Quality Agency completed the first phase of source apportionment studies with Japanese scientists,saying main origins of urban fine particulate matter in 2017.This study examines the concentration and characteristic of fine particulate inUlaanbaatar.The concentration of fine particulate matter is analyzed to examine the properties of the temporal distribution of fine particles.Forty PM_2.5 filter samples were obtained in 2018 and2019 to examine its part of inorganic elements,water-soluble ions and EC,OC.The source contribution list of PM_2.5 in atmosphere of Ulaanbaatar is generated by EPA PMF 5.0 model and CMB model.The results of both from PMF and CMB compared each other.Subsequently,this study presents some suggestion and counter measures for PM_2.5 pollution control in Ulaanbaatar atmospheric environment.This research work reveals the following major conclusions:（1）In 2018,the annual concentration of PM_2.5 in Ulaanbaatar was 74μg/m³ and its valuewas three times higher than the standard particle MNS 4585:2016.The highest concentration was observed in January at the Bayanhsohuu automatic station.In contrast,the lowest concentration was measured at an automatic station of Tolgoit in July.（2）The order of components in autumn’s fine particulate matter isOC>Ca>Si>EC>Al>Cl^->Ca²⁺>SO₄^2->Fe>Mg>NO₃^-K>NH₄⁺>Na⁺>Zn>F>Cu>Mg²⁺>Mn>Pb>Ni>Sn>V>Cr>Mo>Co>As>Hg>Cd>Se.In autumn,Ca is most abundant inorganic element with average concentration 3.88μg/m³,while,Cl^-is most abundant water soluble ion with average concentration 0.92μg/m³ Besides,the order of components in winter’s fine particulate matter is OC>Ca>SO₄^2->EC>NH₄⁺>Si>Al>Ca²⁺>Cl^->NO₃^->Na>Na⁺>Mg>Fe>K>K⁺>Zn>F>Mg²⁺>Sn>Mn>Cu>Pb>As>Ni>Cr>V>Co>Cd>Mo>Se>Hg.In winter,Ca is also most abundant element with average concentration 3.54μg/m³,SO₄^2-is most abundant water soluble ion with average concentration 0.9μg/m³.The high concentration species such as OC,Ca,SO₄^2-,EC,NH₄⁺come from the combustion of biomass.The total content of OC and EC in PM_2.5 was 57.8%of the total,indicating a significant dominance of the combustion of biomass.（3）The results of the analysis of the enrichment factors show that the EF values of metals such as Si,V,Mn,Fe and As were below 1.It means these metals were originating from background soil or natural source.EF values of Al,Cu,Zn,Pb,Mg,and Na were above 1,indicating these metals were derived from both human and natural sources.Also,the EF value of Ni was greater than 10,implying this metal was greatly affected by anthropogenic activities.（4）The PMF analysis shows that the four types of PM_2.5 pollution sources in Ulaanbaatar in2018 are road dust（20.5%）,secondary particles（24.3%）,biomass combustion（10.7%）,and the earth’s crust or earth（44.4%）.Error calculation ways such as bootstrap and displacement were used to provide the probability of results.The displacement diagnostic displayed that no error occurred in the results of PMF.Key species of road dust are Cr,Mo,Ni,V,Co,and Zn,whilst those of secondary particulate are NO₃^-,SO₄^2-,NH₄⁺.Obviously,key species of biomass burning are OC,EC,Cl^-and K⁺.Furthermore,key species of crustal element are F^-,Ca²⁺,Ca,Cu,Fe,K,Al,Hg,and Si.（5）Twenty species including NO₃^-,SO₄^2-,NH₄⁺,Cl^-,Mg²⁺,EC,OC,Al,Si,K,Ca,V,Mn,Fe,Ni,Cu,Zn,Pb,As,Mg,and Na were combined to ambient data and source profiles of CMB.Also,nine profiles such as city dust,industrial dust,coal dust,biomass burning,vehicle exhaust,building dust,soil dust,ammonium sulfate,and ammonium nitrate were included in the origin profile.The CMB investigation displays that the eight PM_2.5 sources of pollution in the city of Ulaanbaatar were city dust（8.5%）,industrial dust（0.7%）,coal dust（31.8%）and construction dust（19.8%）,combustion of biomass（8.4%）,car exhaust（17.7%）,ammonium sulfate（10.4%）and ammonium nitrate（2.6%）.Some marker elements were realized from the MPIN matrix.Marker elements of city dust are OC and Si,while that of biomass burning is OC.Additionally,marker elements of coal dust are Si,Al,and EC,whilst that of vehicle exhaust are EC and OC.Building dust has only one marker element,Ca.Also,ammonium sulfate has two marker elements such as SO₄^2-and NH₄⁺.Ammonium nitrate has two marker elements including NO₃^-and NH₄⁺.（6）Typically,the PMF and CMB models have different categories of pollution sources.The PMF method extracted four factors of fine particles,while the CMB method extracted eight factors of this.For example,road dust as a result of PMF was 20.5 percent of the total mass,while as a result of CMB it was 17.7 percent of the total mass.No many differences were identified in the two methods.PMF biomass burning was 10.7%of the total mass,while CMB was 8.4%of the total mass.An element of the earth’s crust included urban dust,industrial dust,construction dust,and coal dust.The Earth’s crust element as a result of PMF was 44.4 percent of the total mass,while as a result of the CMB it was 60.7 percent of the total mass.Specifically,the PMF result has the name of the source“road dust”,which is identical to the car exhaust gas from CMB.Both PMF and CMB have good results that can better represent the real situation in Ulaanbaatar.Obviously,the CMB result is close to the real situation,although mainland China’s source profiles were used to analyze the PM_2.5 source’s contribution to the CMB.The PMF delivered an initial contribution rate close to the CMB result.