Abstract: The cut-off valve installed in the control rod drive system for CARR is one of the important equipment,which guarantees the safety and reduces the maintenance cost.The function of the cut-off valve is to cut off the passage between the control rod drive system and primary loop,and to prevent the loss of water coolant during maintenance.This paper designed a pneumatic cut-off valve to assist the refueling.With this valve,it is not necessary to empty the water coolant maintenance.Moreover,according to the requirement of ASME Section Ⅲ code,the demonstration test for performance of the cut-off valve was carried out in special test system.The test result showed that the performance of the cut-off valve can meet the design requirement and relevant nuclear codes.