W9Mo3Cr4V high speed steel is treated by composite technology of laser hardening and nitriding. The microstructure and properties of the sample after the composite treatment are investigated by means of X-ray diffraction, scanning electron microscopy, electron probe micro-analyzer, Vickers hardness tester, and friction wear testing machine. The results show that the surface modification layer consists of tempered martensite, retained austenite, Fe3N, Cr7C3, and M2C phases. Laser hardening obviously increases the depth of the nitrided layer, as a result of grain refinement, as well as production of high concentration microscopic defects. Compared to laser hardening and nitriding technologies, respectively, the composite treatment technology can effectively increase the hardness and wear resistance of the high speed steel.