The NC program of foam EPC is complicate. The algorithm provided by UG NC programming system in the CNC tool path arrangement can not control cutter lifting idle path very well in all kinds of concrete conditions. So that it often leads to tool jumping phenomenon，and can not meet the principles of the actual manufacturing process.  Principles of production system were used to design the tool path optimization procedures, a variety of circumstances rule set of tool path optimization was established, four basic concepts of tool path optimization were proposed in which the same-height threshold value ΔZ could adjust the affection of tool path arrangement，and the key problem was encountered in NC auto programming of the foam EPC was solved. The full automation of NC programming was also realized. The results show that the algorithm is doable with the advantages of short knife carrying idle path, reasonable process and high efficiency.