Abstract: This study extends the existing physical random model for a single earthquake to sequence earthquakes as main shock-aftershock by introducing physical relationships of key parameters such as the magnitude, hypocenter and peak velocity between main shock and after shock. Field recorded earthquake records were adopted to determine the coefficients of the probability density function of all these parameters. Then, the superposition method of narrow band harmonic wave groups was utilized to simulate sequence earthquakes, which were compared with real records in terms of time-domain characteristics and response spectrum. The results show that the synthesized ground motions from the proposed model has the close mean value and standard deviation in the response spectrum and non-stationary features in time-and frequency-domains with that of the real records. The proposed model can be used for aseismic performance analysis of civil structures under sequence earthquakes.