Abstract: Based on road roughness profiles generated by harmonic superposition method, the auto-power spectral density and cross-power spectral density characteristics were reversed. According to the coherence function of the left and right wheel tracks, the analytic coherence relation of the phase angles of the corresponding harmonic superposition components in the road roughness profiles of the left and right wheel tracks generated by harmonic superposition method was derived. Taking the coherence of wheel tracks into account, a model of 3D road surface roughness was built. The simulation results of 3D road roughness profile based on Matlab showed that the auto-power spectral densities were almost identical, and the simulation coherence function of the left and right wheel tracks was in good agreement with the specified coherence function, which verifies the high reliability of the phase angle correlation of the harmonic superposition components in computer simulations. It also provides a more reliable simulation model for 3D road simulation.