The depth test of HgCdTe film surface damage layer is important to its processing technology.In this paper,using light interferometer the surface roughness of HgCdTe film was tested,and compared with the depth of damage layer.It was found that the surface damage introduced by the previous process has been completely removed after the roughness value has reached the stable value,and the surface damage is introduced by the polishing process.This method not only can determine whether the damage layer is completely removed,but also has no damage to the test sample.