Stipa baicalensis is one of the main plant communities in grassland in Inner Mongolia and lawn ecosystem in Songnen plain in Northeastern China. The impacts of environmental condition change on C

N accumulation and distribution in Stipa baicalensis were studied. The simulation study shows that the CO_2 concentration in atmosphere enrichment increases root and leaf biomass

and soil drought decreases the root and leaf biomass. The C

N content was markedly increased along with the soil moisture increment

and the C

N content in CO_2 concentration enrichment is higher than that in ambient CO_2 concentration. It can be seen from the C

N distribution that the C

N content in leaf is higher than that in root. The increment of C

N accumulation because of CO_2 concentration in atmosphere enrichment decreases atmospheric greenhouse effect

and this effect would be increased along with the soil moisture sufficient. Under CO_2 concentration enrichment

the C/N ratio in Stipa baicalensis leaf decreases along with soil moisture increment. But

this tendency is not shown under ambient CO_2 concentration. The C/N ratio in Stipa baicalensis leaf is far smaller than that in root. It shows that the leaf nutrition value is higher.