Abstract: OBJECTIVE To establish a method for sterility test of insulin protamine injection. METHODS The method suitability test was performed according to the sterility test method in General Chapter 1101 of Chinese Pharmacopoeia 2015 Volume IV. And optimized the sterility test method of protamine insulin injection included in the Pharmacopoeia. The protamine insulin injection was neutralized with heparin sodium solution without microbial toxicity, so that the protamine insulin injection changed from white suspension to clear and transparent liquid, which was convenient for membrane filtration method. RESULTS Using membrane filtration method, all six positive control test strains could grow normally in the suitability test of sterility test method. CONCLUSION A feasible sterility test method for protamine insulin injection is established, which provides an experimental basis for the revision of the sterility test method for protamine insulin injection included in the next edition of Pharmacopoeia.