In this paper, ultracoarse grained cemented carbide was prepared by in-situ fine grain dissolution-precipitation method with WC, WO₃, Co and C as raw materials. The effects of different WO₃ content on the microstructure and mechanical properties of the alloy were analyzed. The results show that the WO₃ and C could undergo in-situ reduction-carbonization reaction to form fine WC with high activity. In the liquid phase sintering, fine WC dissolution-precipitation could promote the coarse WC grains growth, reducing the micro defects and growth steps, flattening the boundary of WC grains, which could make the morphology of coarse WC grains tend to a fully developed triangular prism. The ultracoarse WC grains with high flattening degree effectively increased the proportion of WC (0 0 0 1) axial plane, improved the hardness, hindered the crack propagation, and strengthened the alloy. So, the alloy with 4.20wt% WO₃ added had the maximum hardness (1085kg/mm2) and transverse rupture strength (2692MPa).