The system produces NC code automatically based on read DXF file，which accomplishes products from design to machine integrative. The component of lap laser system is introduced. The menu of CAD secondary development loaded， parametric drawing and NC code simulation developed，embedded AutoCAD. Analyzed DXF File date form，an interface programming is developed using VC to obtain in graphic informing form AutoCAD. The cut lap welding method is used to welding large arc and large line，which can solve travel not enough one time welding. According to welding processing requirement，welding path is optimized. Engineering example shows the system of NC programming meet demand. The NC program system has good interface and convenient operation.