Five-axis machining area of free surface is proposed by based on ARM9 and Linux open CNC system's overall structure of the CNC system hardware and software architecture. The system adopts the mode of the host computer PC, the lower computer ARM9 development board. PC completes the model of space surface and generates tool path by Simultaneous Multi-objective Optimization Algorithm on Free-form Surface Five-Axis Machining Tool Path and Tool Posture. The lower computer applies MYSQL database to storage and manage cutter location point information. Other modules access the database through ODBC standard interface. ARM9and PC utilize the way of cross-platform socket data transmission, the stepper motors is controlled by the way of constant acceleration - deceleration.