During the welding process of the laser welding machine, the reflectivity of the material changes with the change of the temperature of the workpiece surface, so the pulse shape has an indirect effect on the reflectivity of the material. The laser start function, because the material surface is at room temperature, reflecting slaughter is high: with the increase of temperature, and reflection decreased rapidly; when the material in the molten state, the reflectance basically stable at a certain value; when the temperature reaches the boiling point, and a sharp decline in reflectance. For most metals, the reflectivity is higher at the beginning of the laser pulse action, and the laser welding machine can be used with the optical pulse with a lead tip. The pre peak is conducive to rapid heating of the workpiece, which can improve the performance of absorbing materials, improve the utilization of energy to enjoy, after the main peak pulse gentle can avoid the strong evaporation materials, mainly in the form of the application of pulse low frequency welding. But for the high repetition rate of the welding seam, because the weld is made up of overlapping solder joints, the temperature of the light pulse is high, so it is appropriate to use the flat top wave with the light intensity. For some easy to produce hot crack and cold crack material, can use the three phase laser pulse, so that the workpiece undergoes change process of preheating melting heat preservation, final welding joint welding machine with laser.