Abstract: The construction and main constituent of the integument of Eriocheir sinensis were studied by the methods of histochemistry and atomic absorption methods. The results showed that the integument of E. sinensis was composed of four sub-layers from the exterior to the interior: an epicuticle, an exocuticle, an endocuticle, and a membranous layer. The carbohydrates were deposited in all sub-layers and the collagen fibers were deposited in all sub-layers except the epicuticle. Both carbohydrates and collagen fibers were reabsorbed in premolt stages. The epicuticle and exocuticle were synthesized before molt and the endocuticle and membranous layer were synthesized after molt. The contents of integumental crude protein decreased before molt (D1-D3-4) (P0.05) and were extremely high in postmolt A-B stage (P0.05). The integumental chitinous content showed no obvious variation during the molt cycle (P0.05) except a little increase before molt. The contents of Ca2+and Mg2+ in premolt D1 stage were significantly lower compared with the intermolt stage and other stages in premolt (P0.05) and were the lowest in the postmolt A-B stage (P0.05). There were much Ca2+and Mg2+ in the exoskeleton that the animal moulted. The content of Cu2+ and Zn2+ showed no obvious variation except increased in postmolt A-B stage (P0.05). These results indicated that the structural and constituent changes in integument of E. sinensis are coincident with its molt stages.