Abstract: The effects of slowly cooling to-196 ℃ and being directly placed in liquid nitrogen deep cryogenic treatment（DCT） on the mechanical properties, wear resistance, residual stresses and microstructure of WC-12 Co cemented carbides were investigated by using SEM, XRD and bending tester, etc. The results show that, both DCT processes can improve the bending strength and hardness of cemented carbides, and improve with the extension of the processing time. However, after the treatment time of 72 h, the bending strength and hardness of carbide carbide are no longer improved. The process of slow cooling to-196 ℃ is significantly better than that of liquid nitrogen. Moreover, the bending strength of liquid nitrogen is significantly reduced in the initial stage of ultra-low temperature treatment. The DCT does not change the microstructure morphology, but reduces the residual surface stress of the WC-12 Co cemented carbides, increases the amount of γ-Co→α-Co transition, while improves the wear resistance.