The rice pot experiments were designed under two water management methods, alternation of flooding and dry(FD) and full flooding(FL) with adding 0 g(CKFD/CKFL), 20 g(FD20/FL20), 40 g(FD40/FL40), 60 g(FD60/FL60) crayfish shell powder, to investigate the effects of crayfish shells on cadmium(Cd) accumulation in paddy soil and rice. The results showed that adding crayfish shell powder could increase soil pH under both kinds of water management over the adding amount. Compared with CKFD, the proportion of iron-manganese oxide bound Cd and amorphous Mn oxide decreased after addition of crayfish shell with FD water management for rice at mature stage, thereby increasing DTPA-Cd mass fraction and resulting in increased Cd mass fraction in rice roots, stems, leaves and rice(except FD60 rice). Among them, FD20 and FD40 treatments significantly increased the Cd mass fraction in rice by 38.53% and 40.70%, respectively. The Cd mass fraction of rice under FD water management exceeded the national safety standard(0.2 mg/kg). Compared with FD water management, during the rice ripening period, with the same amount of crayfish shell powder added, FL treatment with crayfish shell powder increased soil pH value, decreased Eh value and pe+pH value, which led to an increase in the proportion of iron-manganese oxide bound Cd, amorphous Fe oxide and amorphous Mn oxide, significantly reduced soil DTPA-Cd mass fraction. Compared with CKFL, with crayfish shell treatment the mass fraction of Cd in the roots, stems, leaves and rice decreased, and the mass fraction of Cd in rice were lower than the national safety standard, and FL60 was the optimal condition.