Titanium alloys are widely used in aerospace industry due to their excellent mechanical properties. Because of their low thermal conductivity, high chemical activity, large friction coefficient and so on, such problems occur during the cutting process as high cutting temperature, large specific cutting force and serious tool wear, leading to low machining efficiency. The cutting force, forms of tool wear; wear mechanics were experimentally studied and analyzed while machining titanium alloy TC4 using carbide tools YS8 and YG8. The experimental results indicated that the tool wear of YG8 influenced cutting force not very remarkable when flank wear smaller than 0.25mm. But when the flank wear was bigger than 0.25mm, the cutting force increased rapidly with the flank wear increased. And the tool wear influenced the cutting force dramatically. The forms of tool wear during machining TC4 using carbide tool were adhesion wear, tool chipping and. The desquamation and chipping of tool caused by adhesion wear were the main reason of the tool failure.