The regimes of non-explosive mechanical treatment of ammonium perchlorate (AP) in high-energy intensity planetary ball mill are found. The changes in the structure and reactivity of AP as a result of mechanical processing were studied by methods of synchronous thermal analysis with registration of mass spectra, x-ray diffraction, microscopy and elemental analysis. Mechanical treatment reduces the particle size from 1000 mu m to a fraction of mu m and leads to formation of agglomerates of submicron particles with sizes of 5-10 mu m. X-ray diffraction analysis shows the absence of the formation of new phases and a substantial broadening of the diffraction lines. As a result of mechanical activation, the temperature of AP thermal decomposition decreases by more than 100 degrees C, accompanied by the rapid release of oxygen at temperatures of 250-260 degrees C, immediately after the phase transformation in AP. The results obtained make it possible to explain the phenomenon of a significant increase in the detonation ability of mechanically activated AP and its mixtures with Al.