Abstract: Based on analyzing H.320 series protocols, a design model of H.320 Videophone is proposed. This paper introduces the design and implementation politics of the system structure and system control. According to the features of H.320 audio and video, the model provides different mechanisms of data acquisition, buffering management, data stream management. It establishes the platform of communication simulation and debug for H.221 module in two ways:communication management on Internet, local virtual loopback route. With adopting the encapsulation technique of object-oriented design, the model provides the general protocol simulation model to speed up the procedure of designing, debugging, testing, updating, and replacing the protocol module. Finally, by using the on-line monitor system of this model, describes and analyzes the video encoding control, bit rate control and lip synchronization of ISDN videophone.