To study the influence of nanometer transition metals on the thermal decomposition of ammonium perchlorate (AP),three kinds of nanometer transition metals (Ni,Cu and Co) were prepared from an aqueous solution by reducing their corresponding metal salts. DTA was employed to test the thermal decomposition of AP in the nanometer transition metal/AP composite. Results indicate that the catalysis of nanometer Ni and Cu increases with the content of nanometer metals and the high and low temperature decomposition peaks have a tendency of overlapping together. The suitable content of nanometer metal Co powder in the composite presentes at about 5%,while the catalysis of nanometer metal Co results in the lowest thermal decomposition temperature of AP in the composite at about 288 ℃. The catalytic capability of nanometer transition metals accordes with the stabilization energy order of their complexes formed with NH₃ as a decomposed intermediate of AP: Co＞Cu＞Ni.