The welding of 316L stainless steel and Q345B low alloy steel belongs to dissimilar steel welding. The defects of welded joints like cracks,pores,slag are easy to appear if an unreasonable welding method is adopted. A welding valve plate developed by an enterprise is taken as an example,the welding methods and technology should be used in practical welding are put forward,which can effectively avoid the common welding defects.