The surface treatment for TC4 alloy was conducted by ME VVA ion implantation method. The changes of surface roughness of TC4 alloy impla nted by varying La + , Mo + volume were measured. It is found that impl antation of the ion results in decreasing the values of height parameters of the surface roughness, and the more the implanted doses increase, the more the parameters decrease, and also the Mo + implantation effects slightly ex ceed La + . The surface morphology of the alloy was improved. The effective mecha nism of the ion implantation on the surface roughness was analyzed with the sput ter theory.