In the substation automation system， the communication protocols adopted by protection relays are varied and the SCADA has to process many protocols simultaneously. The NET framework system model is introduced into the power communication protocol transform system. Its essential characteristic is that a protocol real-time database（P-RTDB） is built between the source protocols and the destination protocols and a common protocol service is provided by integrating the same functions of all kinds of protocol software. The source protocols and destination protocols address P-RTDB or receive and send messages through the common protocol service. So a protocol transform system can process many source protocols at the same time and transform them into their destination protocols. The cost and complexity of the protocol software development is significantly reduced.