Abstract: In this paper, vacuum electron beam welding process of lap joint of GH4169 alloy and electrodeposited nickel plates was carried out, and the effect of fit gap on the structure and properties of the joint was studied. The results show that the larger the lap gap is, the more the filler metal in the gap layer is, and the lower the weld stack height of the upper plate is. The filler metal in the gap layer is mixed and solidified by different alloys. The filler metal has strong convection effect, and the shape and size of the penetration of the lower plate of the weld basically have no change. The hardness of the welded joint decreased from the top, middle and bottom. When the fitting gap of the welded joint is less than or equal to 0.8 mm, the greater the fit gap, the lower the tensile shear resistance of the joint. On the contrary, the larger the fit gap, the higher the tensile shear performance of the joint.