Abstract: Simulation of seismic wave based on Orthogonal HHT is proposed in the paper.Firstly, the problem of energy leakage existing in conventional HHT power spectrum is presented.Integrated with the orthogonal HHT estimating local spectral density of earthquake ground motion, time-dependent power spectrum is used as target power spectrum and the trigonometric series is used to simulate record of nonstationary earthquake ground motion.The sample processes' non-stationary characteristic of intensity and frequency is studied by simulating one acceleration record in El Centro and one acceleration record in Landers. Then, the conclusion on time-frequency character of sample according with that of record is verified by the simulation.Finally, the power spectrum of any sample process dose not necessarily accord with the target spectrum, but statistically, it strictly accords with the target power spectrum.As a result, a lot of earthquake samples having same statistical characteristic as well as the real record can be simulated and it is benefit to history analysis of structural random response.