Abstract��Abstract: We divide 6 indoor cement pools into 2 groups in our study (treatment group I, control group II), each group has 3 parallels. There are 3000 Pagrosomus major in total, each indoor cement pool has 500 Pagrosomus major (initial average weight 70.0 g). Soft pellet and fresh trash fish surimi were respectively added into treatment group and control group to explore the effect of the infection rate of Cryptocryon irritans to Pagrosomus major. The results show that Pagrosomus major were be infected by Cryptocryon irritans after the addition of both soft pellet and fresh trash fish surimi, however the infection rate were showed significant difference (P<0.05). Fresh trash fish surimi feed will much more easier lead to a spread and outbreak of Cryptocryon irritans infection than soft pellet. The major infected areas are fish gill filaments and body surface.