Magnesium-based hydrogen storage materials (MgH2, Mg2NiH4, and Mg2Cu-H) were prepared and their structures were determined by XRD and ICP investigations. Mg2NiH4 has a monoclinic crystal structure and Mg2Cu-H is a mixture of MgCu2 and MgH2. The effects of magnesium-based hydrogen storage materials on the thermal decomposition of ammonium perchlorate (AP) were studied by thermal analysis (DSC). It was found that magnesium-based hydrogen storage materials show obvious boosting effects on the thermal decomposition of AP. The thermal decomposition peak temperature of AP was decreased, while the heat release of the decomposition of AP was increased. It was revealed that the effects of magnesium-based hydrogen storage materials on the decomposition of AP become stronger with increasing content. The influence mechanism on the thermal decomposition of AP is suggested as follows: hydrogen released from magnesium-based hydrogen storage materials and Mg, Ni, or Cu react with the decomposed products of AP.