Abstract: The main pipeline is one of the key equipment in a nuclear power plant. With a relatively large thickness, the main pipeline is checked and accepted according to the RCCM, a French standard. Therefore, problems such as disqualification of the negative film during radiographic examination, misunderstanding of the check and acceptance standard, confirmation of the defect and the like often happen. And, these problems might threaten the welding quality of the main pipeline. This article elaborates the RCCM, analyzes the advantages and disadvantages of various radiographic examination methods and tries to optimize the main pipeline radiographic examination method. It also aims to facilitate the correct understanding of RCCM and helps to make a correct evaluation of the defect through graphic representations and examples.