Abstract: Ni based coating was prepared on 45# steel substrate by plasma spraying. After the remelting treatment of coating by TIG welding, the microstructure of the remelted coating was observed by scanning electron microscope (SEM), and the EDS spectrum of the crack was analyzed. The results show that the remelting current has an obvious influence on the crack tendency of the remelted layer. At the current of 50 A, the remelting layer is well formed and there is no crack. However, the current increases to 60 A and 90 A, the crack becomes more and more serious. In addition, the EDS spectrum shows that there are many B and Si elements in the crack. On this basis, the causes of cracks were analyzed and the solutions were proposed.