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In this study,we performed a highly time-resolved chemical characterization of non-refractory submicron particles (NR-PM1) in Beijing by using an Aerodyne high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS).The results showed the average NR-PM1 mass concentration to be 56.4 ± 58.0 μg/m3,with a peak at 307.4 μg/m3.Due to the high frequency of biomass bing in autumn,submicron particles significantly increased in organic content,which accounted for 51％ of NR-PM1 on average.Secondary inorganic aerosols (sulfate + nitrate + ammonium) accounted for 46％ of NR-PM1,of which sulfate,nitrate,and ammonium contributed 15％,20％,and 11％,respectively.To determine the intrinsic relationships between the organic and inorganic species,we used the positive matrix factorization (PMF) model to merge the high-resolution mass spectra of the organic species and NO+ and NO2+ ions.The PMF analysis separated the mixed organic and nitrate (NO+ and NO2+) spectra into four organic factors,including hydrocarbon-like organic aerosol (HOA),oxygenated organic aerosol (OOA),cooking organic aerosol (COA),and biomass bing organic aerosol (BBOA),as well as one nitrate inorganic aerosol (NIA) factor.COA (33％) and OOA (30％) contributed the most to the total organic aerosol (OA) mass,followed by BBOA (20％) and HOA (17％).We successfully quantified the mass concentrations of the organic and inorganic nitrates by the NO+ and NO2+ ions signal in the organic and NIA factors.The organic nitrate mass varied from 0.01-6.8 μg/m3,with an average of 1.0 ± 1.1 μg/m3,and organic nitrate components accounted for 10％ of the total nitrate mass in this observation.