For the purpose of seeking a kind of technology which can purify black and odorous river sewage rapidly and effectively, take water from Xinhe River as the experimental object, the effect of compound microbial inoculant on river sewage purification was investigated. The results showed that COD_mn、NH₃-N and TP decreased after adding the compound microbial inoculant, this was as a basic judgement when the compound microbial inoculant should be add again. 48 days later, the removal rate of COD_mn、NH₃-N和TP at Fengshou River and Douzuhuang River reached 46.38% and 46.94%、70.68% and 69.79%、71.65% and 87.95% respectively, and the odor was eliminated obviously. The compound microbial inoculant had good performance on river sewage purification.