To provide quality guaranteed real-time video stream in Internet is one of the main contents of multimedia application. But packet loss often occurs in data transmission across Internet, if no recovery measure is adopted, a drop in video quality will occur. Current research focuses on how to improve the quality of video stream and guarantee its real-time character. This paper studied the influence of packet loss on video quality based on MPEG-4 stream, presents a retransmit-important-data-based error recovery method, in order to improve the quality of real-time video stream. And according to RTP protocol, proposes a new CR-RTP protocol to support the retransmission of video data.