The catalysis of nano Cu powder on the thermal decomposition of HMX and RDX was investigated by using DSC,PDSC and TG-DTG. The results show that thermal decomposition of solid phase for HMX and liquid phase for RDX is accelerated apparently due to the nano Cu powder. The solid phase thermal decomposition temperature of HMX decreases 25.5 ℃ when the mass ratio of HMX with nano Cu is 1：1. The liquid phase decomposition temperature of RDX accelerates from 239.1 ℃ to 220.9 ℃. The decrease of exothermic enthalpy is due to the dilution and dispersion function of the nano Cu powder.