【Objective】To investigate the effect of different amounts of straw returned to the field on soil CO2 emission under deep returning conditions, and to provide theoretical basis and data support for the research of straw resource utilization and carbon sequestration and emission reduction in agricultural soils. 【Method】This experiment was conducted in the field micro-area, and three experimental treatments were set according to the different amount of straw returned to the field, namely CK (no straw returned). T1 (full straw returned, 10500 kg·hm-2); T2 (double straw returned, 21000 kg·hm-2). The CO2 emission rate of soil was measured by LI-8100A automatic soil carbon flux analyzer (Li-Cor, Lincon, NE, USA), and its influencing factors were investigated. 【Result】①Straw returning can increase the rate of CO2 emission, and the double and full amount of straw returning were significantly greater than that of no straw returning, which showed an increase of 92.53% and 61.95%. ②The CO2 emission rate of each treatment reached the maximum at 30℃(Temperature) and 24% (Moisture), and the two-factor fitting model of temperature and moisture is better (R2 = 0.488~0.583), indicating that the carbon dioxide emission rate is jointly regulated by temperature and moisture. ③The residual dry matter of straw was about 25.54%~28.21% after 100 d of field return, and its degree of decomposition was significantly positively correlated with the cumulative CO2 emission; and the decomposition of straw increased the soil SOC, MBC, TP, and TK contents, which promoted the CO2 emission. 【Conclusion】The characteristics of soil CO2 emission were affected by temperature, water content and other soil nutrients, and the increase of straw returned to the field could enhance soil nutrients, increase CO2 emission and promote soil respiration.