The invention provides a device and method for strengthening foil connection strength under laser loading. The device comprises a laser loading system, a control system, a heating system, a welding system, a clamping system and a three-dimensional mobile platform system; the laser loading system comprises a focusing lens, a lens support, a lens height adjustor, a reflector and a pulse laser; the control system comprises a computer, a laser controller, an air pressure controller, a heating controller and a three-dimensional mobile platform controller; the temperature system comprises a heating plate; the three-dimensional mobile platform system comprises a three-dimensional mobile platform and a right-angle base; the welding system comprises a restraint layer, an absorbing layer and a workpiece; and the clamping system comprises a workpiece, an air cylinder, a die driving device and upper and lower dies. According to the device and method, under the heating condition, by loading lasers, two layers of foil can be subject to impact welding and clamping at the same time, and the connecting strength of the foil is strengthened; and the die driving device in the device can drive the movable upper die to move left and right, the self-locking effect can be achieved, and the working efficiency is improved.