Real-time control is very important in CNC system. Ther are lots of problems about development of control system, The idea of developing the Windows CE-based Open-architecture CNC system is proposed in This paper. With the characteristics and trend of Open-architecture CNC system, we must focued on real time control of CNC system, so we analyze the system architecture and its real time performance, and a Windows CE.NET-based software architecture of this system is also presented. Finally the developing plan of device driver on the operating system is discussing emphatically.