Abstract: Different solid solution and aging process heat treatments were done to 17-4PH stainless steel according to the actual measured thermal expansion curve. It was found that the final aging process could improve the proportional limit, Rp0.02 and plastic of the materials by studied the microstructure and mechanical properties after heat treatment. The forming process of reverse austenitic was determined with metallographic analysis combined with X-ray diffraction method and the reverse austenite content formed at different final aging temperature was measured by X-ray quantitative method. The results show that the amount of reverse austenite in 17-4PH stainless steel produced in the final aging process increased as the final aging temperature going up.