Based on high communication cost of Siemens S7-300 and WINCC and  limited investment of small typed project, S7-300 through PC ACCESS software constructing OPC channel in WINCC was designed to realize the communication of upper and  inferior. The technology was easy to connect and with little investment of hardware, and could read-write S7-200 series all storage areas of PLC, was suitable for slow and low real-time demand and limited investment funds system.