Abstract: By using FORTRAN language, the fitting of the target response spectrum of ground motion method based on phase difference spectrum model and random phase spectrum was compiled. Through analysis of characteristic parameters of synthetic time, this paper probes into the influence of random number selection and determination method of phase spectrum on the peak of synthetic time and duration. It uses random phase spectrum and phase difference spectrum to set an example and calculate the time history and response spectrum of ground motion. In addition, it compares and analyzes change of the characteristic parameters-PGA, PGV, EPA, EPV, 90% energy duration and 70% energy duration of synthetic time history when two methods adopt the same random number. The results of analysis show that there are differences among peak values and energy duration of synthetic time history. However, the peak value doesn't change too much. The analysis on characteristic parameters of synthetic time history of 30 selected groups of random number in above-mentioned two methods has proved this point. It shows that PGA and PGV have little difference, and EPV has some difference, but energy duration of the time history have large difference between two methods, energy duration T_95-5,T_80-10 based on phase difference spectrum model are higher than those of time history of random phase spectrum method, EPV is slightly lower than those of time history of random phase spectrum due to the impact of different phase spectrum.