In laboratory, Anodonta woodiana(AW)and Corbicula fluminea (CF)were fed with 3 algal species of Microcystis aeruginosa, Chlorella pyrenoidosa and Scenedesmus obliquus, and the effects of algal specie, shellfish body size and density on the feeding rates were studied at approximately 20℃ of water temperature. Three-way analysis of variance (ANOVA) showed that:There was significant difference among three algae in feeding rate for CF but was not for AW; Shellfish body size and density had effects on feeding rate of them; Interaction of body size and density on feeding rate for CF was found, however not observed for AW; The feeding rate of the two shellfishes both decreased significantly with increasing density; The feeding rates of the small-sized individuals were significantly higher than those of large-sized ones for CF reared at 2 relatively low densities and for AW at all three densities; No significant differences in feeding rate were found for CF reared at 2 relatively high densities; The correlation between feeding rate and dissolved oxygen (DO) concentration for CF was obviously higher than that for AW; Shellfish body size and density rather than feeding with different algae influenced the DO in water container. The results showed that the stress degree by low DO might cause the differences between the two shellfishes in interaction of body size and density on their feeding rate and the large-sized individuals of CF are more tolerant of low DO than the small-sized ones.