Abstract: More and more the third generation nuclear power plant manufacturing are substituted for the second half generation nuclear power plant manufacturing in China gradually, and the standard of nuclear power plant manufacturing according to ASME code will be used more and more than RCC-M code. This paper analyses the welding variables for welding procedure qualification basing on listing welding procedure qualification of one equipment manufacturing, base metal and welding material assignments, postweld heat treatment and range of thickness of base metal qualified. It concludes that assignments are based essentially on comparable base metal characteristics, such as composition on weldability, welding material and mechanical properties and so on, each welding variables has its range of qualification, and range of qualification welding variables shall be performed totally according to ASME.