A new method is developed to preparate HMX by nitrolysis of DPT with nitrating agent HNO₃-P₂O₅-NH₄NO₃.The content of HMX in HMX/RDX mixture obtained from the nitrated products were determined by means of Hitachi 635 type HPLC.The results indicate that the yield of HMX by this method is approaching to that from nitration with acetic anhydride. This is a valuable progress in HMX synthesis without using acetic anthydride.