In order to compare and analyze the shock wave sensitivity of a new aluminum explosive, the initiation behavior of two aluminum explosives (HL-10-L-1 and HL-109-L-1) under long period and low value impulse loading were studied using big gap test and numerical calculation. The critical gap thickness and ∫p²dt of nondetonation and nonviolence reaction were obtained. Analysis shows that adopting ∫p²dt value to infer the reaction behavior of explosive under low value pressure pulse is more reasonable than the critical gap thickness.