Abstract: It is found that the standard of shear tensile test of resistance spot welding is not uniform. The material used was galvanized Q235 stainless steel. The trend of failure load, failure displacement and energy absorption with the change of the width of the specimen were detected. The reasons for this change is oxplained in the mechanical point of view. There is a critical width when these three variables reach constant values. If the specimen width is not enough, the specimen deforms greatly. Nugget rotation results in a opening force, leading to the tensile shear measurement is less than the actual strength of the joints.