A CNC machine tools networking system was designed and realized based on the Ethernet communication. Unified communication protocol, data format were adopted in the Ethernet communication，but the protocol, data format in communication between network terminal and machine tools were converted to another style which could be identified by the machine tool. So different machine tools could be accessed to the same network to realize unified management. The machine tool condition realtime monitoring, processing and working log management, machine program management were implemented. Good effect has be gained during actual operation.