Abstract: The overlap welding experiments of 316 stainless steel with 0.2 mm thickness by using pluse fiber laser were carried out.Effects of laser peak power and pluse width on the trail of the back was investigated.The result showed that as the peak power and pluse width being increased,the strength of the spots increases,and the trail of the back becomes serious.At the peak power of 200 W and the pluse width of 3 ms,the strength of the spots reached 22.4 N,and no rail on back of the spots.The analyses results of the cross sections showed that the welded spots with the penetration depths of 0.3 mm meet the requirements of high strength and no trail on the back.