Abstract: The process of linear friction welding for TC4 titanium alloy was studied by orthogonal experiment. The effects of process parameters on the weld formation were analyzed through observation of the morphology of weld cross section. The results show that the macroscopic morphology of linear friction welds could be divided into the "X"-type, "I"-type and "V"-type. Friction pressure has the greatest effect on weld formation followed by frequency and amplitude. Under the same other conditions, the reduction of amplitude makes the weld area narrow, and reduces the fluidity of plastic weld metal; when the increase in friction pressure is less than the increase in the frequency, it is helpful to acquire a better weld; although increasing frequency with large amplitude enhances the heat input, but the heat loss is big, which is harmful to obtain a weld of good quality.