The ASME code and RCC-M code are widely used in the design and manufacture of class 1 nuclear power equipment. In general,both of them are used simultaneously in the fabricating of primary device by manufacturer. Welding is the most critical and important process of the nuclear power equipment manufacturing. In this paper,the comparison of the class 1 nuclear component welding in ASME code and RCC-M code is introduced by respect of standard structure,requirement,welding temperature,heat treatment and the weld test coupons. The difference of standard application is analyzed from the perspective of users,which lays a foundation for formulating reasonable welding process.