Abstract: In order to clarify the effects of straw decomposition agents in tobacco-planting soil, simulated pot culture experiments were conducted to analyze the contents of soil available nutrients, organic carbon (SOC) fractions as well as their evaluation indexes after the application of rice straw combined with decomposition agents. The results showed that compared with only applying chemical fertilizer, the contents of soil particulate organic carbon (POC), easily oxidized organic carbon (EOC) and dissolved organic carbon (DOC) increased by 36.89%, 30.77% and 75.73% respectively after applying rice straw combined with chemical fertilizer. The contents of soil available nitrogen (AN), available phosphorus (AP), total organic carbon (TOC), POC, EOC and DOC increased by 17.42%-28.33%, 49.94%-55.68%, 10.46%-15.20%, 39.32%-74.27%, 54.36%-64.62% and 84.58%- 124.27% respectively after applying rice straw combined with decomposition agents. The application of rice straw combined with chemical fertilizer or decomposition agents significantly increased the effective rate of soil labile organic carbon and decreased the antioxidant capacity of SOC, and the latter treatment was more effective. Principal component analysis indicated that the application of rice straw combined with decomposition agents increased TOC content, improved the effective rate of soil labile organic carbon and decreased the antioxidant capacity of SOC. There was no significant difference in the effects between the applications of rice straw combined with decomposition agents containing dominant microorganism of bacteria + fungi (XZ) or bacteria + fungi + actinomycetes (XZF) on soil available nutrients and SOC fractions.