A playing back channel simulator which uses the real measurement channel data can provide reliable performance verification of the wireless communication systems. In this paper, an efficient channel data processing algorithm to implement a playing back channel simulator in a software is suggested. At first, an algorithm to efficiently reduce huge volume of original channel data is presented and a multi-rate signal processing algorithm is also proposed to fit the bandwidth of the measurement channel to the bandwidth of the input signal. As a result, we can find that the playing back channel simulator using these new algorithms has low processing complexity while preserving the characteristics of the original channel from the simulation results.