Mold heat treatment is an important process to ensure the performance of the mold, and has a direct impact on the manufacturing precision of the mold, the strength of the plastic mold, the working life of the mold, and the manufacturing cost of the mold. Mold heat treatment is to play the potential of mold materials and improve the performance of the mold. The performance of the mold must meet: high strength, including high temperature strength, injection mold ，resistance to thermal fatigue, high hardness (wear resistance) and high toughness, and also requires good machinability, including good polishability. weldability and corrosion resistance, etc. The deformation of the plastic mold after heat treatment is generally considered to be caused by cooling, which is not true. Molds, especially complex molds, have a great influence on the deformation of the molds. The comparison of some mold heating processes shows that the heating speed is faster and tends to produce larger deformation.