Abstract：The rain-flow counting method is discussed in this paper. Based on the loading spectra of a vehicle obtained from a standard test ground testing, a method is proposed for treating the actual measured data for load histories. The examples of the compression and extrapolation of loading spectra based on rain-flow counting are given, where the time scale is reduced remarkably. Then different roads in the test ground are combined to simulate the customer road. This research can pave the way for road simulation in a further step.