Abstract: To understand the CO2 emission from soil crop system as influenced by crop growth and application of fertilizer ,pot and field experiments were carried out during Bima-1、Yannong –15 and Shannong-11 wheat growing seasons. Black chambers were used to take gas samples within a closed soil-crop system. Use LI-6400 type portable light and measure apparatus (U.S.A. ) to determine the soil CO2 releasing amount in growth period of crop. And we tested water stress of soil, the dry matter weight, photosynthetic rate and the above-ground biomass, the ratio between root and canopy, the high of wheat, chlorophyll content, the area of flag leaves .The results showed that the application of fertilizer can improve the CO2 emission of soil. The temperature of soil and water stress of soil were main factor for determining change law of release amount of CO2 from soils and those rising and falling bring out the increase and decrease of release amount of CO2.In certain range of nitrogen fertilizer application rates, the dry mater weight, photosynthetic rate, the high of wheat, chlorophyll content, the area of flag leaves and the above-ground biomass. The root affected the CO2 emission of soil, and show significantly positive relationship.