The wind turbine rotor is alloy steel 42CrMo and Q235B dissimilar steel structure,the SMAW and MAG hybrid welding are used to perform the welding experiments. Through metallographic microscope,universal mechanical testing machine and scanning electron microscope analysis,the microstructure properties and appearance of fracture of the welded joints are observed and analyzed.The results show that the increase of welding heat input will reduce the bending properties and low temperature impact properties of welded joints of 42CrMo and Q235B,in the actual welding of motor,the welding heat input,preheat temperature and interpass temperature should be controlled;the microstructure,mechanical properties and the appearance of impact fracture and other technical indicators of welded joints in the 42CrMo and Q235B dissimilar steels prepared by a welding technology with a small heat input all meet the relevant standards,which provides strong technical support for the welding of motor rotor.