Abstract: In order to alleviate the problem of end face cracking and failure of pure oxygen burner hot part-outer nozzle in coal chemical industry, the microstructure and phase composition of the failed material on outer nozzle surface were studied,and the failure reasons of different damage forms were summarized. Base on this, UMCo50 alloy was overlaid on the same base material by TIG welding. Based on the range analysis method of multi-factor orthogonal experiment, the surfacing process was optimized. The results show that the optimal surfacing process parameters are welding current of 120 A, surfacing speed of 10-11 cm/min, interlayer temperature of（60±10）℃, and surfacing layer number of 2-3. The optimal process has been experimentally verified in actual production, providing theoretical reference and technical support for the optimization of hot parts’ surfacing repair process.