Abstract: For the sake of studying the influence of a rear barrier on the shock initiation of shielded explosives, shock initiation of explosives with and without a rear barrier by fragment was analyzed using the numerical simulation software. The simulations show that the shock wave reflection of the rear barrier can lead to higher pressure in the explosive near the rear barrier thus lowering the impact velocity required to detonate the explosive. But with the increase of the thickness of explosive, the influence of the rear barrier gradually declines. The material of the rear barrier has great influence on the amplitude reflection shock wave, but the critical velocity required to detonate the explosive between different barrier materials is not big.