Cadmium is ubiquitous in the human environment and has been recognized as one of the most deleterious heavy metal pollutants. Pollution of sea by cadmium as a component of industrial wastes leads to a considerable increase in its concentration in aquatic animals. But, considerable difference in the sensitivity to cadmium among shellfish has been reported. This work was an attempt to investigate cadmium bioaccumulation in various tissues of bay scallop Argopecten irradians and the factors influencing cadmium bi oaccumulation during simulated pollution. Cadmium in the seawater entered the gill of bay scallop by passive pervasion. The Langmuir isotherms were employed to describe the gill surface binding activity of cadmium. The binding capabilities were 2.12 μmol·g^-1 dry wt. The cadmium exposure results indicated: the bioaccumulation amount in tissues increased with the addition of cadmium concentration in seawater. When the cadmium concentration in the seawater was 2 μmol·L^-1, after 4 days, the bioaccumulation amount in the gill was (1.5±0.52) μmol·g^-1 dry wt and the accumulation velocity was (0.375±0.13) μmol·（g·d）^-1. At the same time, the bioaccumulation amount in the viscera was (7.19±0.83) μmol·g^-1 dry wt and the accumulation velocity was (1.79±0.21) μmol·（g·d）^-1. But the accumulation number in the muscle was the least ［(0.005±0.0009) μmol·g^-1 dry wt］. During of 19 days exposure in seawater containing 2 μmol·L^-1 cadmium, the bioaccumulation in the gill, viscera and muscle increased with the extension of feeding time. After 14（336 h）days, the cadmium accumulation in the gill, viscera was close to saturation. But the cadmium in the muscle was far from saturation. In fact, when the storage capacity limits of the liver and kidney are reached, cadmium accumulation in muscle is stimulated. The reported results show that salinity affects cadmium accumulation in various tissues of the tropical fiddler crab Uca rapax. In the present study, we found that there was not significant effects of salinity on cadmium accumulation in various tissues of Argopecten irradians（P>0.05）. When the bay scallop was bred in unchlorinated, aerated well water, the cadmium accumulated in the body was eliminated significantly. The excretion rate in the gill was 38.3%.