Abstract: Mechanical and chemical responses of small-caliber shaped charge initiating a typical explosive reactive armor were simulated by using AUTODYN-2D software. Influences of charge diameter, liner angle, liner wall thickness and standoff on jet tip velocity and initiation parameter were obtained. By analyzing the initiating phenomenon of jets against ERA and the pressure change of the explosives that are set between ERA, effective methods of comprehensively judging whether the explosives explode or not are proposed. The results would provide a useful guide for the antitank front tandem warhead charging designing.