Abstract: In order to explore the interaction process and mechanism of bullet impacting a gelatin target with hard/ soft composite armor，the penetration of 7.62 mm bullet into composite armor and gelatin is numerically simulated using an FEA method，and the typical phenomena of impacting process and the dynamic response of gelatin target are analyzed. The simulation results show that the formation of the ceramic cone results from the compressive and tensile stress waves. The obvious segmentation and inflection points display on the curve of projectile acceleration. The acceleration reaches its maximum when the projectile penetrates into a ceramic faceplate. The second inflection point appears when the projectile penetrates into PE rear plate. The multi-peaks appear on the velocity curve of PE rear plate due to multiple interfaces on protection layer：When the projectile reaches the maximum acceleration，the first peak appears，and the first pressure peak appears on gelatin interface；the second peak appears when the projectile penetrates into PE rear plate. The propagation of pressure wave in gelatin presents the basic form of spherical wave， and the pressure peak propagation complies with the law of exponential decay.

Key words: ordnance science and technology, bullet, numerical simulation, hard/soft composite armor, gelatin, penetration