The cold fusion at room temperature is used to repair the shaft of automatic transmission. In the experiment, the low-carbon steel, the high-carbon steel and 65Mn steel were selected as restorative materials. The microstructures of shaft repaired with different materials were observed by the scanning electric microscope (SEM) after the shafts were repaired. The results show that the microstructure of shaft which was repaired by the high-carbon steel and 65Mn steel is martensite that has high hardness and better wear resistance. The interface of the matrix and filled material is metallurgic combine. The cold fusion can improve the surface properties of the matrix when the suitable material is selected as restorative material.