Abstract: With the application of metal materials being more and more extensive,demands for the theory-developing and smelting technology of materials are higher and higher. The high temperature metallographic technology provides a new research method. The process of phase transition in the deposited metal of ER410 Ni Mo was observed through a high temperature laser confocal microscope,which can help to intuitively understand the phase transition process of martensite stainless steel. According to in-situ observation results,the phase change initiation and termination temperature of each phase were obtained,and the characteristics of melting,crystallization and solid phase transformation in martensite stainless steel were described in detail. It is shown that CLSM has unparalleled advantages and application prospects in the research of solidification of materials,solid phase change,and inclusions aggregation.