Direct straw returning and straw carbonization returning are the main measures of straw returning. Because of the differences in structure and nature as well as returning process between straw and straw biochar, the soil respiration and soil carbon budget after returning must have significant differences. In this study, outdoor pot experiment was carried out to study the response of soil respiration and carbon budget to straw and straw biochar returning and its possible mechanism. The results showed that soil respiration of straw biochar returning [mean value 21. 69 µmol.(m2.s)-1] was significantly lower than that of direct straw returning [mean value 65.32 µmol.(m2.s)-1], and its soil organic carbon content ( mean value 20. 40 g . kg-1) and plant biomass (mean value 138. 56 g) were higher than those of direct straw returning (mean values 17. 76 g . kg-1 and 76. 76 g). Considering the carbon loss after the biochar preparation process, its soil carbon budget was also significantly higher than that of direct straw returning, so it was a low carbon mode of straw returning. Direct straw returning significantly promoted soil dehydrogenase activity, soil β-glycosidase activity and soil microorganism quantity, leading to higher soil respiration, but straw biochar did play an obvious role in promoting the microbial activity index. Easily oxidizable carbon (EOC) and biodegradability of straw biochar were lower than those of straw, which showed that straw biochar had higher stability, and was more difficult to degrade for soil microorganisms so its soil microbial activity was generally lower, and could be retained in the soil for a long time.