With the raw material of the precision forging M42 spray formed high speed steel, the orthogonal experiment under different parameters was used to optimize the technology of heat treatment and analyze the material’s microstructure, hardness, and flexural strength and the evolution law of carbide in different heat treatment systems. Results show that the best preservation temperature for quenching was 1180℃, and the temperature for temper which should be repeated 3 times and 1h for each time was 540℃. In this system, Rockwell hardness of M42 can reach to 67.2HRC, while flexural strength can be 315MPa.During the process of heat treatment, M₆C carbide was largely affected by the change of quenching preservation temperature. When the quenching temperature was 1190℃, M₆C carbide fully melted, and dispersedly separated after tempering.