Predation is a key determinant in the regulation of species abundance and composition in marine benthic communities. The effect of predator density, size, sex, prey density, size, and temperature, substrate condition on predation was investigated using the crab (Sesarma haematocheir) and bloody clam (Scapharca subcrenata). The results indicate that crabs displayed the type II functional response, S. subcrenata seeded at high density improved the survival rate significantly. The feeding rates of crabs decreased significantly when shell length of the clam reached 20 mm. The feeding rates increased as crab size increased, and the survival rate of the clam decreased significantly. Interference competition between conspecifics improved the clam survival rate significantly as crab density increased. Male crabs with stronger claws leaded to higher deaths of S. subcrenata. Releasing of S. subcrenata in spring and autumn at relatively low temperature improved survival rate. Substrate of complexity and heterogeneity provided more spatial refuges for the clam survival, which reduced the loss from predation.