Abstract: In order to study the physiological function of aquaporin AQP, the aquaporin 2 gene (ptaqp2) of Portunus trituberculatus was cloned, which is full-length 4126 bp, encodes 522 amino acids and has the conserved domain and functional domain of aquaporin gene family. Cluster analysis showed that ptaqp2 gene belonged to C-AQP gene of aquaporin gene family. The results of tissue expression showed that the expression of ptaqp2 was the highest in eye stalk, the highest in intestine and muscle, and the lowest in hemolymph. The expression of ptaqp2 gene was significantly different in different molting stages, and the highest expression was in the early stage of molting. Under the stimulation of Molting Hormone (MH), the expression of ptaqp2 gene was up-regulated in muscle, intestine and stomach. By knocking down the expression of ptaqp2 in the early stage of molting by RNAi technique, it was found that it could significantly delay the molting process. It has been preliminarily proved that ptaqp2 gene plays an important role in molting of Portunus trituberculatus.