To clarify the effects of different treatments of Chinese horseshoe crab genetic engineering antimicrobial peptide on the survival rate of rainbow trout, in this study, the antimicrobial peptides were applied by soaking and mixed feed in the larvae and adult stages of rainbow trout respectively. In order to verify the effects of different treatments of antimicrobial peptides on immune indexes of rainbow trout, the whole fish tissues of the larvae and the serum and head kidney tissues of the adult fish were collected respectively to detect the levels of the immune-related enzymes of SOD, ALP, CAT, IL-1β, IFN-γ, and TNF-α. The results showed that:soaking 10 times with 84 U/mL antimicrobial peptides of the larvae of rainbow, the immune-related enzyme levels of the experimental group were significantly higher than those in the control group on the 4th day after soaking, such as IL-1β and IFN-γ were extremely significant (P<0.01), while the others were significant (P<0.05); on the 15th day after soaking, the experimental group was still higher than the healthy fish of control group, IL-1β and IFN-γ were extremely significant (P<0.01), while the others were significant (P<0.05). However, the levels of immune-related enzymes in the sick fish of control group were decreased significantly than those of the experimental group. SOD, ALP, IL-1β, IFN-γ were extremely significant (P<0.01), while the others were significant (P<0.05). The survival rate of larvae in the experimental group was up to 95.1%, while the control group was only 29.9%. The adult fish were carried out from two aspects:mixed feed test and soaking test. The results showed that, the optimal dosage of the mixed feed was 50 mg/kg, the optimal concentration of the soaking was 84 U/mL, and the optimal soaking time was 3 min. Compared with the different treatments, it is found that the effects of soaking on the immune index of rainbow trout were most significant at the stage of the larvae. It may be related to the type of antimicrobial peptides, the mode of action and the outbreak characteristics of farmed rainbow trout. The results of this study will provide experimental basis for the application of antimicrobial peptides in rainbow trout culture.