The invention discloses a method for improving the smoothness of a weld joint of a metal vacuum cup and an automatic welding equipment for the method. The method comprises the steps that the weld joint data are collected; the weld joint data are screened; local polynomial fitting is carried out; and welding is controlled. The automatic welding equipment using the method comprises a data measuring device, an automatic welding equipment body and a four-power independent conveying one-way circulation device, wherein the four-power independent conveying one-way circulation device is used for conveying and positioning the metal vacuum cup to be welded; the automatic welding equipment body is a laser welding device; the four-power independent conveying one-way circulation device comprises a base 200 and conveying guide rails 201; one-way driving mechanisms are arranged under the conveying guide rails; and shunting mechanisms of sliding bases arranged at the joint parts of the adjacent conveying guide rails 201. According to the equipment and the method, the welding quality of a port of the metal vacuum cup can be improved, the welding speed of the port of the metal vacuum cup can be increased, the labor intensity can be reduced, and a wide application market and huge economic benefits can be achieved.