The third Chinese National Arctic Research Expedition (3rd CHINARE-Arctic in 2008) was carried out from July to September 2008.During the survey,numerous sea water samples were taken for CO2 parameter measurement (including total alkalinity TA and total dissolved inorganic carbon DIC).The distribution of CO2 parameters in the Western Arctic Ocean was determined,and the controlling factors are addressed.The ranges of summertime TA,normalized TA (nTA),DIC and normalized DIC (nDIC) in the surface seawater were 1 757- 2 229 μmol·kg-1,2 383-2 722 μmol·kg-1,1 681-2 034 μmol·kg-1,2 119-2 600 μmol·kg-1,respectively.Because of dilution from ice meltwater,the surface TA and DIC concentrations were relatively low.TA in the upper 100 m to the south of 78°N had good correlation with salinity,showing a conservative behavior.The distribution followed the seawater-river mixing line at salinity ＞30,then followed the seawater mixing line (diluted by river water to salinity =30) with the ice meltwater. The DIC distribution in the Chukchi Sea was dominated by biological production or respiration of organic matter,whereas conservative mixing dominated the mixed layer TA distribution in the ice-free Canada Basin.