The invention discloses a composite polishing method based on a laser and a plasma. The workpiece to be machined is fixed on the working table of the polishing system, then the laser beam is convergedto the surface of the workpiece to be processed through the laser polishing device to form a laser beam focal spot, and then a normal-pressure plasma beam is generated through the plasma polishing device to impact the surface of the workpiece to be processed to form a plasma impact region; adjusting the laser beam pointing direction and the plasma impact direction to enable the laser beam focal spot to be overlapped with the plasma impact region, and carrying out composite polishing on the surface of the workpiece to be processed; moving the focal spot of the laser beam through a multi-axis moving platform, and the plasma impact composite area finishes the polishing of the whole surface of the workpiece to be machined. According to the method, the modification and composite etching effects of the surface of the material on the surface of the material are achieved by utilizing the plasma in the ultrafast laser processing process, the surface machining quality is improved, and the bottleneck problem that the surface machining quality of the ultrafast laser is not high is solved, so that the high-quality and high-efficiency fine polishing of the surface of the material is realized.