Abstract: HLA/RTI is a new standard for distributed interactive simulation. It defines a framework for the interoperation between federates. Aiming at the application of audio transmission in distributed virtual battlefield environment, the audio stream is regarded as a federate. The simulation object model is defined according to the HLA/RTI standard, and the interaction of federates is realized through API of RTI. Thus RTI may work as the protocol at the application layer to realize and control the audio stream transmission in distributed interactive simulation.