Abstract: The purification process and antimicrobial activity of bovine protamine extracted from bovine testis were studied,for purpose of improving purity and utilization of bovine protamine.Crude bovine protamine was gained by ultrasonic- assisted extracting with 5.48% sulfuric acid solution,precipitating with 95% cold ethanol,washing with acetone,ether. Bovine protamine was purified by SP- Sepharose Fast Flow ion exchange chromatography and Sephacryl S-100 gel filtration chromatography,and the yield was 3.92%.The molecular weight was 19 ku analyzed by SDS- PAGE.The result of antibacterial test indicated the total number of colonies of fresh beef,sauced beef,fresh bean curd and sauced bean curd dealt with bovine protamine purified were greatly significant less than them dealt with crude bovine protamine( p < 0.01),and respectively decreased 86.44%,85.77%,83.39%,89.82%.Bovine protamine purified had strong antimicrobial activity,which showed bovine protamine was a well natural food preservative.