Method and system for performing laser-stirring composite penetration fusion welding on thick plate

The invention discloses a method for performing laser-stirring composite penetration fusion welding on a thick plate. The method comprises the following steps: step 1, providing a first workpiece anda second workpiece; step 2, accurately butt-jointing and clamping the first workpiece and the second workpiece; step 3, providing a laser-stirring composite welding system, wherein a laser welding head and a stirring needle are arranged into a row horizontally in a welding direction; step 4, starting the laser-stirring composite welding system, wherein a laser beam perpendicularly radiates the upper surface of a workpiece, and focusing spots of the laser beam are averagely distributed on the first workpiece and the second workpiece according to the size; and step 5, when a temperature acquiredby a temperature sensor reaches or exceeds a temperature value of workpiece melting, enabling the stirring needle to downwards screw into a welding pool, and enabling the stirring needle and the laser beam to synchronously mo