During pre-service inspection（PSI） of a certain CPR1000 nuclear power plant,a lack of fusion is found in the weld between main coolant line（MCL） and outlet nozzle safe end of steam generator（SG） which complies with the requi-rements of radiographic testing（RT） during erecting,and the defect is repaired. For the problem about the validity of the main primary system hydraulic test with the effect of welding repair of MCL weld, based on comprehensive analysis of the relevant items about hydraulic testing in RCC-M code,RSE-M code,Section Ⅲ and Section Ⅺ of ASME code,a solution for nondestructive testing is proposed,which is an examination comprising two volumetric examinations or an examination comprising a single volumetric examination,that ensures the validity of hydraulic test of the main primary system.