Abstract: JMF(Java Media Framework)is a socket that introduce multimedia audio and video stream into JAVA and Applet programs.The major difference between network based multimedia teaching system and ordinary multimedia application is that it contains not only audio and video streams,but also the screen and the teachers hand writing data stream.The realizations of JMF API and JMF RTP API in network based teaching system is discussed,it is a better solution in network class recording system.