Abstract: To resolve nowadays real-time speech communication in LAN and speed up the application of the low rate speech coding technique, a real-time speech communication system applied in LAN based on low bit rate speech coding and network transmission technique is designed. The modules of sampling,compression, transmission and post-processing about speech signal are included in this systerm. The software implementation method for above modules is given based on the technique of network transmission and computer multimedia. The computer simulation result indicates that the real-time communication can be perfommed stable and reliable in this system and the system has the potential value for LAN application.