The shock initiation/ignition of Cylindrical Charges Covered with thin Aluminium Shell (CCCAS) by steel fragment impact was experimentally and theoretically investigated. The critical specific kinetic energy criterion and threshold for the shock reaction of CCCAS were obtained. During the experiments, the response characteristics of CCCAS by steel fragment impact were studied. Then the surface microstructures of explosives were examined by scanning electron microscope (SEM). According to the ex-perimental phenomena and existing theories, a calculation model for critical criterion for the shock reaction of CCCAS was developed by dimensional analysis. Based on the calculation model and numerous tests of cylindrical charges covered with 3 mm aluminium shell under the impact of steel fragments with the mass from 1.0 g to 2.0 g, the critical specific kinetic energy threshold for the shock initiation of CCCAS was obtained.