The in-situ Preparation of WC-6Co composite powder was subjected to dry-bag type cold iso-static pressing without any pre-treatment (The pressing pressure was 1000 bar and the holding time was 15 s). Ultra-fine YG6 cemented carbide was prepared by sintering the pressed blank in a low-pressure sintering furnace at a (sintering temperature of 1360 ℃ with 40 min sintering time, and it was kept under 5 MPa pressure holding for 20 min). To analysis the morphology, metallography and physical mechanics properties of the YG6 cemented carbide, The results showed that: abnormal grain growth can be observed from the Ultra-fine YG6 cemented carbide, the average grain size of the WC alloy is 0.8 μm; The hardness HV30 is 2150±10, which is higher than the conventional Ultra-fine YG6X cemented carbide. Then, the composite powder of WC-6Co was produced to ultra-fine size YG6 cemented carbide through processes of wet-milling, pressure type spray drying, binder adding, extrusion forming, low-pressure sintering. Through the analysis of the effects of different grain growth inhibitor ratios, ball-milling time, extrusion pressure and sintering temperature on the properties of the alloy were investigated by testing the mechanical to the physical properties of the carbide, the results showed that: when 0.3 wt % VC and 0.8 wt % Cr3C2 were added, wet milling 48h , extrusion at 24 MPa pressure and sintering temperature of 1340 ℃, the produced Ultra-fine YG6 cemented carbide has homogenous WC grain size, No WC grains with abnormal growth can be observed from the Metallographic diagram of the YG6 cemented carbide. The average grain size of WC alloy is 0.4 μm, and the grains are in polygonal shapes with relatively round outlines. The strength and hardness of YG6 cemented carbide prepared under these conditions are the highest. The TRS of YG6 cemented carbide is 2250±20 MPa, and the HV30 is 2260±10. Intergranular fracture, along the WC and WC grain boundary fracture or WC and Co grain boundary fracture can be observed from the morphology of fractures.