Gonadotropin (GtH) protein was purified from the pituitary of Russian sturgeon using fast protein liquid chromatograph (FPLC). A total of 4.6 mg of Russian sturgen GtH in dry weight was obtained. The purified protein was analyzed by SDS-PAGE electrophoresis. Two subunits of GtH were separated by reversed-phase high-performance liquid chromatography (rpHPLC). The molecular weight was determined through mass spectrograph. The α subunit was 15 603 ku and the two β-subunits were 14 338 ku and 14 694 ku respectively. Rabbit anti-sturgeon GtH polyclone antibody was prepared; purified GtH was labeled by ¹²⁵I using chloramines T as labeled antigen; then the sturgeon GtH radioimmunoassay （RIA） method was set up using the goat anti-rabbit γ-globulin as the second antibody . After inducing ovulation, changes of serum GtH levels were detected. The secretion peak of female fish ovulated successfully was sustained from 12 to 16 hours after first inducing injection and the serum GtH levels were increased significantly compared with control group and un-ovulated fish. The effect time of LHRH-A was related close to the serum GtH levels.