Abstract: Researched on micro-hardness of W9Mo3Cr4V high speed steel (HSS) cutting tool material with the impact of pulsed magnetic field. The HSS samples were magnetized with directional pulse on a self-build platform for the magnetic treatment test. The effects of different pulse magnetic field strength, frequency and magnetization time on the micro-hardness of HSS material were studied, and the changes of HSS material microstructure under the action of pulse magnetic field were analyzed by observation metallurgrical structure. Test results indicate that the appropriate pulse magnetization parameter can improve the specimen micro-hardness of HSS material obviously. Pulsed magnetic can make part of the retained austenite translate into hard and brittle martensite inside the metallic material, which makes martensite content increase, and material organization become more uniform.