This study investigated the impact of the different straw decomposing microorganism inoculum (SDMI) on straw decomposition and rice yield in a paddy soil along the Huai River, Huoqiu County of Anhui Province, in which four treatments were designed, which included straw returning with optimized NPK fertilization then applied SDMI NO.1 (SFD1), or SDMI NO.2 (SFD2), or SDMI NO.3 (SFD3) or nothing (SF). No significant differences occurred in total decomposition rates of straws among different treatments in two consecutive years, but significant differences were found in straw decomposition rates in the first year. Straw decomposition rate increased by 70.59%, 262.5%, and 93.33% in SFD2 compared with SF, SFD1, and SFD3, respectively. Among all treatments, SFD2 had the highest rice yield in two consecutive years (8 592.84 kg/hm²and 7 538.70 kg/hm², respectively, P<0.05). Rice yield and straw decomposition rate had the highest correlation (Pearson correlation coefficient was 0.45 in the first year and 0.48 in the second year). All treatments had significant effects on soil microbial biomass, but no clear pattern was found among different treatments. In addition, soil microbial biomass C/N ratio was the main attribute to determine the decomposition rate of straws. In conclusion, our study suggests that the application of different SDMIs can promote straw decomposition and increase rice yield, and SDMI No.2 is most promising due to its highest efficacy in stimulating soil microbial communities, accelerating straw degradation and promoting rice growth.