In this paper, performance of 8-ISDN traffic for the buffer size which is requested of important parameters in switch/multiplexer of B-ISDN with multimedia traffic is analyzed. Multimedia traffic is modeled as a traffic, which is composed of poisson distribution traffic and burst traffic with exponential/geometric ON time duration(Burst duration) Performance of traffic which is modeled as a multimedia traffic is analysed and buffer size, can provide the high quality service, is presented for the cell loss probability. It is simulated using event scheduling approach method which is provided by simulation package, PC SIMSCRIPT II.5. Simulation program is composed of PREAMBLE, MAIN, INITIAL, ARRIVAL, DEPARTURE and STOP·SIM modules. Specially, in case of mixed traffic simulation, ARRIVAL module is composed of ARRIVAL I and ARRIVAL II, and cells are generated independently by each module.