Abstract: In order to fulfill the ability of machining capability of complex surface structure which was facing intersecting groove of large-scale intersecting pipes,to ensure that the included angle of welding at any point on the intersecting line was the same.Firstly,the mathematical models were built by using the method of analytic geometry for the intersecting line,groove curve and it's expansion line;secondly,the mathematical models were transformed into a space curve through the CNC programming software,and the groove surface model was built based on this;finally,the machining of intersecting groove surface was completed by using CNC machining programming and CNC milling machine.