Vacuum sintering densification behavior of nanoscrytalline WC-10Co composite powders produced by mechanical alloying was studied. The results show that the increments of sintering temperature and time promote densification process which is faster during 1 2751 300 ℃, and almost the whole densification can be achieved at (about) 1 300 ℃ after 15 min. The increasing content of VC and Cr_3C_2 composite grain growth inhibitors is not beneficial to improving densification. The new grain growth inhibitor A was proved to inhibit grain growth more effectively. The density of 14.48 g/cm~3 and the grain size of about 180 nm can be achieved at 1 375 ℃ after 30 min from nano-grained WC-10Co-0.8VC/Cr_3C_2-0.2A composite powders.