Objective To screen a kind of microorganism which is low poisonous for living creature but has high molluscicidal effect. Methods The Xanthobacter autotrophicus from the soil where Oncomelania hupensis lived were detached, then its molluscicidal effect against the snails were studied by the immersing and contacting methods, respectively. Results The death rates were 1.3%-95.0% immersed for 24 to 72 hours in the different density liquids (1?106,2?106,3?106,4?106 cfu/ml). The LD_~50 immersed for 48 hours was 2.6?106 cfu/ml. The death rates had obviously positive relationship with the immersing time and the density of the liquid. Conclusion The liquid which contains more than 106 cfu/ml Xanthobacter autotrophicus has a stable molluscicidal capacity, and the immersing method is better than the contacting method.[