Abstract: Vegetation plays an important role in CO2 fixation,O2 release carbon circulation of atmosphere and land ecosystem.And it is the main feedback and regulation system and it has important ecological function and ecological service value.Based on the investigation on the grassland resources in Dulan County and the related materials,the net primary productivity of different grassland vegetation types was calculated.And the mass and values of CO2 fixation and O2 release were assessed according to equation of photosynthesis,reforestation cost method,method of carbon duty and industrial method of making O2.The results indicated that the annual net primary productivity of grassland vegetation in Dulan County was 364.04 ×104 t per year.The quantity of fixed CO2 and released O2 were 593.38×104 t per year and 436.85×104 t per year.Using reforestation cost method and carbon duty method,the value of CO2 fixation by vegetation in Dulan County was 10.338 5×108 yuan per year.Using reforestation cost method and industrial method of making O2,the value of released O2 was 16.445 7×108 yuan per year.Among the mass and value of CO2 fixation and O2 release of different grassland vegetation in Dulan County,the dry desert had the highest contribution rate,followed by alpine grassland,mountain grassland,swamp and alpine meadow.