This article take CNC grooving machine as the study project, take the design of open control system based on PC+motion control card as study method, take use of the powerful motion control function and abundant DLL function library of MPC08SP motion control card, apply Visual C++ 6.0 to the development of the underlying process, gives the design of open CNC system of grooving machine, which satisfies the real-time performance and accuracy of control system.