The invention relates to an automatic pole lug welding device which comprises an installation plate, a second connecting plate, a wall plate and a pole lug unwinding and winding device. The second connecting plate is fixed to the wall plate. The installation plate is installed above the second connecting plate. The pole lug unwinding and winding device is fixed to the left end of the installation plate. A guiding block used for guiding a pole lug is arranged behind the pole lug unwinding and winding device. A first air cylinder used for compressing the pole lug is arranged above the guiding block. A pole piece pulling device is arranged behind the guiding block. A cutting-off device is arranged behind the pole piece pulling device. A pole lug pinching device is fixed to the inner side of the cutting-off device. A pole lug flattening device is arranged behind the cutting-off device. A pole lug centering device is fixedly arranged on the outer side of the pole lug flattening device. A bottom anvil welding device is arranged behind the pole lug flattening device. A welding device is arranged above the bottom anvil welding device. The automatic pole lug welding device is ingenious and reasonable in structure, capable of automatically cutting the pole lug with the fixed length, and capable of welding the pole lug with the fixed length to a pole piece, and the pole lug welding efficiency is improved.