Abstract: Pyrosequencingtechnique was used to analyze and compare bacterial diversity in the mantle of healthy and incised symptoms of Patinopecten yessoensis, respectively. For the two samples, 20872 and 16333 effective sequences were selected and utilized to perform bacterial diversity analysis, respectively. Bacterial diversity and richness in the incised samples were higher than that in the healthy samples. The effective sequences acquired from both samples included eight known phyla bacteria, i.e., Proteobacteria, Firmicutes, Actinobacteria, Bacteroidetes, Cyanobacteria, Planctomycetes, Spirochaetes and Tenericutes, among which the front seven phyla were present in the two samples. Proteobacteria was absolutely dominant in the mantle of healthy P. yessoensis accounting for 97.7% of the entire bacterial community, and Firmicutes was the subdominant group accounting for 0.8%. In contrast, the most abundant bacterial group in the mantle of incised P. yessoensis was Firmicutes, accounting for 52.2% of the entire bacterial community, and the sub-dominant was Proteobacteria accounting for 47.7%.