Abstract: Four experiments were respectively conducted to determine the tolerance of broodstock, larvae and juvenile of bay scallop (Argopecten irradians) to different concentrations of chlorine dioxide for safe use in disease prevention and cure. Each experiment had six treatments with three repetitions according to the concentrations of chlorine dioxide. Each experiment last out for 24h, and data of mortality rate were respectively determined at 12h and 24h. The results showed that the safe concentrations of chlorine dioxide for broodstock, D larva, eyebot larva and juvenile were respectively 20 mg/L, 5 mg/L, 10 mg/L and 10 mg/L.