Laser ultrasonically combined cutting was proposed based on ultrasonic vibration cutting with laser heating assisted cutting. A series of experiments were conducted in conventional cutting, ultrasonic vibration cutting, laser heating assisted cutting and laser ultrasonically combined cutting YG10 cemented carbide with PCBN tools. The tool wear characteristics and tool wear mechanism were observed by using digital microscope with super depth, the energy spectrum analysis was carried out in worn areas of tools by scanning electron microscopy (SEM). The experimental results indicate that the average flank wear of PCBN tool obtained by laser ultrasonically combined cutting is reduced by almost 57.5%, 46% and 41.3% respectively when compared with that by conventional cutting, ultrasonic vibration cutting and laser heating assisted cutting, therefore the tool life is obviously lengthened. The main wear types are crater wear, flank wear and tipping for PCBN tools in cutting YG10 cemented carbide. And the adhesion, oxidation, phase transformation and micro dissociation are the main reasons for the wear of PCBN tool in laser ultrasonically combined cutting YG10 cemented carbide.