Abstract: Resistance spot welding technology is introduced into the welding process of tooth and back material during the preparation of bimetal band saw blades. The shear test was used to study the effect of welding current on the strength of dissimilar steel welded joints of M51 powder metallurgy high speed steel and RM80 high strength steel. The metallurgical microscope and scanning electron microscope were used to observe the interface microstructure and shear fracture behavior of welded joints under different welding currents. The results show that with the welding current increasing, the strength of the welded joint increases first and then decreases. When the welding current is lower than 800A, the shear fracture of the joint is mainly at the weld interface position. When the welding current is higher than 800A, the joint shear fracture is mainly in the heat affected zone of the RM80 steel side. When the current is 800A, the shear strength reaches the maximum of 420.8 MPa. By fitting the interface strength and the strength of the softened zone,the failure of the welded joint was analyzed.