The effect of stud welding principle and parameters on welding quality is described in detail. Through statistical analysis of stud welding defects of front floor sheet,it is found that magnetic blow is the main cause of stud removal welding. The reasons of welding magnetic blow are analyzed and discussed from the aspects of stud size,part shape,ground connection method and fixture design. By increasing the fixture support,adjusting the grounding line and optimizing the lifting height,the welding defects caused by magnetic blow in the stud welding process of sheet are solved,and the stud welding quality is improved.