Abstract: Aiming at the defects of known number and the requirement for weld defect ratings, the design of a program was proposed to use Windows application design principle for JB/T 4730.2—2005 steel, nickel, and copper melt pressure equipment welding butt welding joint for the purpose of classification of round defect levels evaluation criteria. Through establishing the application documents, inserting a dialog box in the menu, pressing the button control add function, editing box control function and group box function, and followed by the procedure of debugging and compiling, it shall generate a visual interface. By inputting the mother material nominal thickness and round number two variables, the defect evaluation system shall automatically show you the level of defects. The experimental results show that the automatic rating program design is reasonable, the operation result is accurate.