Abstract: During the pre-service inspection of a certain CPR1000 reactor pressure vessel（RPV）,unacceptable defect is found in the weld between outlet nozzle and flange-nozzle shell which complies with the requirements of ultrasonic testing（UT） during manufacturing.To solve the problem,the comparison of UT technique employed during manufacturing and PSI has been demonstrated.It is proved that the immediate cause of problem is that the acceptance criteria of manufacture according to RCC-M code has been applied to UT technique of PSI,and the root cause is the differences of the sizing method and the grouping requirements for defects between manufacturing and PSI.On account of PSI is intended to act as a zero point for in-service inspection,the view point is presented that unacceptable defects found during PSI,if possible,should be re-examined and accepted in accordance with the testing method and acceptance criteria of manufacturing.