The application of turning centers for complete machining greatly increases production efficiency by means of introducing new machining possibilities. At the same time, it makes the generation of NC process plans more complicated and as a result the current process planning methods often fail in dealing with the new requirements. Based on agent theory this paper presents a new strategy for distributing a complex planning task to different relatively small planning units, so-called agents, which are defined considering both machine and workpiece structure. Instead of a central algorithm the agent based planning method generates NC process plans through some cooperative activities between different agents. The activity model and the cooperation rule are also discussed in detail.