Abstract: The development trend of industrial Ethernet and embedded system technology is introduced. And the simple and open Modbus/TCP protocol is embedded into the Rabbit 2000 controller. The reliability and real time performance are improved by modifying the parameters of the TCP layer and presenting a group of implementation rules. In addition, the development system Dynamic C is adopted to implement the module and function of Modbus/TCP. Finally the main function codes are extracted to simplify the protocol and to enhance the performance of the controller.