A design method for a satellite data traffic system was developed by using a band-pass sampling theorem, the simulation system sampling rate was designed, from which the lowest equivalent carrier wave formula was deduced. The deduced formula could be applied to other simulation systems. At the same time, equivalent design methods for time and frequency of the practical system were presented. According to the system function structure, the system software frame and running threads were studied. Finally, corresponding function models were realized. Two work modes including an independent running and a network controlling were provided to simulate integrally functional models required by the transmitter and receiver of the satellite data-traffic system including radio modulation. Based on the evaluation model, the frequency spectrum, eye pattern and relation of Bit Error Ratio(BER) and Signal to Noise Ratio(SNR) were presented. Experimental results show that when the SNR is equal to -2.52 dB,the BER of this simulation system is 10-5. The simulation results are basically in agreement with theoretical values.