Abstract: Aiming at the reliability and safety problems of low firing rate and hidden dangers of UXO at large incident angle of active small caliber projectile fuze, the response characteristics of firing mechanism of small caliber projectile impact fuze were studied. In this paper, the dynamic model of the firing mechanism with large incident angle was established, and the simple criterion of the action of the firing mechanism was obtained. Based on the numerical simulation method, the dynamic response process of the firing mechanism with large incident angle under multiple working conditions, including different impact speeds, incident angles, rolling angles and target plate thicknesses, was simulated. The effectiveness of the numerical model was verified by shooting tests. The analysis results show that the random rolling angle of the hitting ball is one of the important factors affecting the functional reliability of the firing mechanism when hitting the target at a large incident angle; the smaller the amplitude of the counter impact force, the slower the response time of the axial resultant force, which is unfavorable to the reliable function of the firing mechanism. Meanwhile, it is found that with the increase of the incident angle of the fuze and the thickness of the target plate, the failure mode of “jamming” of the guide sleeve and the firing pin appears.