Abstract: In the welding crafts of the main body casting of underground exploration robot, there are several important factors affecting its service life, such as pressurized treatment pressure, heat treatment time, cooling time and polishing time. We make system experimental study on fatigue of the casting, analyze important factors and test results using response surface methodology, elaborate the fitting mathematic model, ultimately determine the maximum service life and value of each factor of the main body casting of underground exploration robot, when the pressure treatment pressure is 8 MPa, the heat treatment time is 15 h, the cooling time is 5.1 h, the polishing time is 48 s, the maximum value of the service life is 10^6.95 hours.