The rapid assessment product of earthquake intensity is an important basis for judging the disaster situation during the " black box period" of emergency response after a destructive earthquake. Based on the aftershock sequence within 2 h after the M6.9 earthquake in Menyuan, Qinghai Province, we used a ground motion attenuation model with the shortest fault distance to rapidly evaluate the earthquake intensity in this paper. The results showed that the intensity distribution obtained by using the aftershock sequence within 30 minutes after the M6.9 mainshock can preliminarily determine the hardest stricken area and the disaster areas, but the scope of disaster areas is smaller than the actual survey result. The intensity distribution obtained by using the aftershock sequence within 1.5 h is consistent with the field investigation results, and the calculation results using the aftershock sequence within 2 h have no obvious change. The seismic intensities obtained using the relocated aftershock sequence are more accurate than those obtained from the conventional aftershock sequence, but a suitable relocated method needs to be selected. In this earthquake, the intensity range evaluated by using the aftershock sequences shows a characteristic that the accuracy is higher with growing intensity, and the hardest-hit areas determined using the result are accurate. The proposed method enriches the existing system of rapid intensity assessment, but its applicability and conditions need to be further studied.