Abstract: We divided 6 indoor cement pools into 2 groups in our study (treatment group I,control group II),each group had 3 parallel experiments. There were 3 000 Pagrosomus major in total,and each indoor cement pool had 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 Cryptocaryon irritans on Pagrosomus major. The results showed that Pagrosomus major were infected by Cryptocaryon irritans after the addition of both soft pellet and fresh trash fish surimi,however the infection rates were showed significant difference (P<0.05). Fresh trash fish surimi feed could much more easily lead to a spread and outbreak of Cryptocaryon irritans infection than that of soft pellet. The major infected areas were fish gill filaments and body surface.