A kind of real-time communication protocol named Message-Stream Test Protocol(MSTP) and based on reflective memory network,is designed for the Simulation Testing Environment of Avionic Software to solve the common communication problem of periodic and asynchronous communications.The MSTP is designed on SCRRAMNet;the layout of memory is introduced;and the sending and receiving process are described.The testing result demonstrates that the design is feasible.At last,a more precise model of system cost is presented.