Modbus Serial (ACII/RTU) OPC Server 320 was developed by OPCTechs Technology Corporation in June. 2005. According to the standard OPC 3.0 Specification, we developed the packaged software for our extended customers especially in the automation fields. It is suitable in the integration fields in every walk of life. Modbus protocol is one of the most popular communication protocol in the world today. As the new devices create, the modbus protocol should be embedded by the device makers. Modbus protocol let the engineers fast and easily to integrate devices to the automation software. The devices such as power meter, water leakage machine, generator, UPS … etc. They all inborn provide the Modbus communication protocol.