Abstract: To investigate the efficacies and mechanisms of immunocastration by using gonadotropin releasing hormone analogues (GnRH-A) in animals. The GnRH-A antigen emulsion was made by adding incomplete Freund′s adjuvant after GnRH-A was combined with bovine serum albumin(BSA). 30 rabbits were injected with GnRH-A antigen, the testis length and weight as well as body weight of the immunized rabbits were measured，GnRH antibody titer and testosterone concentration were detected through ELISA. There was a significant difference of the testis lengths between two EGs groups(P<0.01)，antibody levels of EG-Ⅱ group was higher obviously than that of EG-Ⅰ; the serum testosterone concentration between EG-Ⅰ and EG-Ⅱ groups were remarkably different from 7 to 16 weeks(P<0.05 )，the body weight and average daily gain of EG-Ⅱ group were the biggest and significantly higher than that of EG-Ⅰ group as well CG(P<0.05). The testis development，serum GnRH antibody titer and testosterone concentration of experiment rabbits changed obviously after immunization of GnRH-A and adding another injection would strengthen castration effects.