To study the change of coaxiality of rotor shaft during laser cladding, a numerical simulation of the rotor shaft was carried out by ANSYS Workbench, and the temperature field and structure field of the rotor shaft were simulated and analyzed by indirect coupling of transient temperature field and transient structure field. The temperature distribution of the rotor shaft during laser cladding was obtained from the results of the temperature field. The maximum temperature is 2350°C, and the final temperature converges to about 2100°C. Then, the results obtained from the temperature field are entered into the structure field as loads, and the change of coaxiality of rotor shaft during laser cladding is obtained. Finally, the laser is used to clad Fe60 powder on the 45 steel rotor shaft, and the coaxiality of the rotor shaft after cladding is measured by Taylor cylindricity meter. The measurement results are basically consistent with the simulation results, and the error is <10 %. It lays a good foundation for exploring the cladding mode or track that can maintain better coaxiality of rotor shaft in the process of laser cladding and is of great significance for the repair of damaged rotor shaft.