Laser polishing is a special processing technology with prospect of application, particularly used for processing small size parts with high hardness which can′t be achieved by conventional methods. 38CrMoAl has much superiority including high surface hardness, high fatigue strength and good resistance to overheating resistance. And it is widely used in mechanical machining, such as piston bolt and lathe spindles. 38CrMoAl can be polished by laser in a more efficient and environmental way. 38CrMoAl is micro-polished by YAG laser (1064 nm). Surface roughness of 38CrMoAl steel is analyzed by a three-dimensional topography instrument. Based on the surface morphology characteristics before and after polishing, the better processing parameters of the voltage at 790 V, pulse duration at 0.17 ms and the polishing position above the laser focal plane 3 mm are obtained. By using the micro-polishing method, the surface roughness of the metal can be decreased from 142.02 nm to 79.10 nm which have fallen by 44.3%.