Abstract: Using the principle of oscillograph on the analysis of hardware,we introduce the assistant application of real-time monitor observer in the development of audiovisual communication system.In this paper,we emphasize on introducing it's use in the development of videophone based on ISDN H.320 series protocols.Using the observer,we define kinds of"probes" independent of real communication system.Using these probes to monitor running system,dynamical parameters are snatched.Base on these parameters,the system characteristics are realized.Thus we can find the system's"bottle-neck" as soon as possible and adjust system design and optimize system.In the development of video module,we define parts of on-line monitoring windows,from which we can get statistic data;with which we adjust arithmetic in video coding module and decoding module.The same application in video module can help to control coding efficiency in video coding module,and help us to choose accurate video format in communication.Software probes in the application of the buffer in thread help us to know whether the buffer size is suitable,and make policy that we read and write data to those buffers.For example,according to on-line observing,we finally choose quantity and size of the audio buffer to achieve the best lip-synchronization result.