An improved stochastic finite-fault method was used to simulate the M_w 6.6 earthquake that occurred on August 8, 2017, in Jiuzhaigou, Sichuan, China. A variation of the stochastic finite-fault method, considering the dynamic corner frequency, was used to overcome the corner frequency. It explains the effect of a given slip distribution on the corner frequency of each subfault. A comparison of the response spectra (damping ratio 5%), spectral ratio (simulated values/observed values), and model deviation demonstrated that the improved corner frequency performs well for the whole periods, especially in short periods from 0.2 to 1 s. Similarly, the revised duration model and the site-amplification factor were applied to simulate the ground motion during the Jiuzhaigou earthquake, and then the response spectra were obtained. The duration of the nine near-field station recordings matched well with the simulated ground motions, and the peak ground acceleration (PGA) of most of the stations matched well with the observed PGA. In the short periods (T < 1 s), a small difference is observed between the simulated response spectra and the observed spectra for most of the stations. However, the response spectra were overestimated within the period range (0.05–10 s). Generally, the simulated ground motions obtained by using the improved model matched well with the observed ground motions, which could be considered the basis for earthquake-resistant design during the postdisaster recovery and the structural dynamic analysis of the Jiuzhaigou region.