Real-time transport protocol is analyzed in this paper. Some questions related to real-time transport are studied. These questions mainly involve coding/decoding of audio and video data, transmission protocols and congestion control. Then, it puts forward a MPEG-4 video transport model based on RTP, explores the payload format of RTP and packetization algorithm, suitable for MPEG-4 video bit-streams to achieve simultaneously both high efficiency and robustness for Internet MPEG-4 video. At the same time, In allusion to the characteristic of streaming media Transmission on IP network , The thesis makes improvement on the algorithm of congestion control based on AIMD through coming up with an autoadapt threshold adjust scheme ,in order to reduce surge of sending ratio, improved the QoS transmission of audio and video information.