The invention discloses an electrode lug welding device and a work method. The electrode lug welding device comprises a single-axis mechanical hand, a linear guide rail A, a linear guide rail B, a sliding plate and an ultrasonic welding machine. The single-axis mechanical hand is installed on the side, away from a welding position, of a bottom plate, and a screw nut is arranged on the single-axis mechanical hand. The linear guide rail A is installed on the side, close to the welding position, of the single-axis mechanical hand, and a sliding block A is connected to the linear guide rail A in a sliding manner. The linear guide rail B is installed on the side, close to the welding position, of the linear guide rail A, and a sliding block B is connected to the linear guide rail B in a sliding manner. The sliding plate is located above the linear guide rail A and the linear guide rail B and is fixedly connected with the screw nut, the sliding block A and the sliding block B. The ultrasonic welding machine comprises an installation plate, a rack, an air cylinder A and a welding machine upper module. By means of the electrode lug welding device and the work method, an electrode lug can be limited in a left-right manner, limited in a vertical manner and limited in a forward manner, pleating of the electrode lug is prevented, and the welding quality of the electrode lug is ensured.