ABSTRACT -- Application of Computer Numerical Control (CNC) System in industrial works which used to be done by Manual Machines is crucial for strengthen industry competitiveness by improving efficiency, productivity and quality to meet international standard. Thus, development of technology in this field should be conducted urgently. This paper gives an overview of previous development of CNC controllers and demands from industry. Many consideration aspects for designing of CNC controller is then given.Based on Open Architecture concept, a pattern of development of CNC controller is proposed. The proposed system is PC-Based CNC Controller which is highly efficient for working in graphic environment and high-level processing, it also utilizes motion controller chip for position servo-loop control. The main idea is to develop two sub-systems which response for different aspects of CNC controller, those are, Multi-Axis Control (MAC) sub-system and Man-Machine Interface (MMI) sub-system. When MAC sub-system responses for real-time tasks such as Trajectory Planning, Axis Synchronization and PLC operation, MMI sub-system does high level processing tasks such as high-level interpretation, tool-path compensation, simulation and so on. A development example of CNC controller for plasma cutting machine is then given. Further development works include, adding more Open-ness standard to the controller such as standard fieldbus interface, developing own algorithms for position servo system which could be implemented by software CNC for machine operations which are not so complicate, together with development of other value added MMI software such as simulation, Nesting and software for interfacing with Computer Process Control System and CIM