Abstract: In response to the frequent occurrence of welding seam height differences in the Miebach laser welding machine during the operation of a company′s pickling and rolling mill unit, the welding seam height difference phenomenon was classified into two types, i.e.overlap type and thickness difference type, and the causes were analyzed. The results indicate that the size of the joint gap between the strips and the variation of the strip length have a significant impact on the welding seam overlap, and the thickness of the strip and the height of the lower support wheel have a major influence on the welding seam thickness difference. By controlling the parallelism of the shear blade side surfaces within 0.05 mm, ensuring the clamping force of the clamp, optimizing the defocusing amount from the original-5 mm to-7 mm, strengthening the control of strip quality defects, and ensuring the accuracy of key equipment such as the double cut shear, clamps, support wheels, and pre-rolling wheels, the daily numbers of welding seam height difference alarms has been reduced from 9 times to 3 times.