Explosion interruption mechanism with horizontal rotor is still in static balance when it is in malfunction, so common dynamic characteristic simulating method is not suitable for use. In this paper, after analyzing the loading conditions of rotor, it was pointed out that the primary reason of malfunction was that the spring-loaded side pin blocked the movement of rotor, herein the loading condition of rotor was improved by changing its structure. Theory analysis and experimental results show that the improved rotor can arm reliably, and the reliability of fuze is also improved.