Welding method and welding system for battery shell

The invention relates to a welding method and system for a battery shell, the shell comprises a shell body used for surrounding the periphery of a battery cell and a cover plate used for sealing the end of the shell body, and the welding method is used for welding the cover plate and the shell body. The welding method comprises the steps that a welding path is obtained, and the welding path is at least divided into a first section and a second section which are connected in sequence; a welding head is controlled to conduct constant-speed welding on the first section; and the welding head is controlled to conduct uniform acceleration welding on the second section from the end point of the first section. When the battery shell and the cover plate are welded, the welding speed of the second section is made to be the uniform acceleration larger than the welding speed of the first section, and laser energy input of the welding head to the rear section can be reduced, namely linear energy is reduced. And even if th