On August 8, 2017, an earthquake occurred near Jiuzhaigou County, Sichuan Province with M_S7.0. The earthquake happened near the northeast boundary of the Bayan Har fault block where the geological structure is very complicated. The earthquake is located at the transitional position from the north boundary of the Bayan Har fault block with a left-lateral tectonic environment to the east boundary with a strike-slip tectonic environment and many strong earthquakes happened near this field in history. The Jiuzhaigou earthquake sequence belongs to mainshock-aftershock type with an extremely low seismic activity of the aftershocks. Although the time intervals between the aftershocks with M_L ≥ 4.0 is abnormal in a short time after the mainshock, the seismic activities of the aftershocks returned to normal soon after that, and the h value of the sequence and the apparent stress of the aftershocks show that the characteristics of the sequence is in accordance with the mainshock-aftershock type. The b value of the sequence is 0.84, the magnitude of the largest aftershock deduced from the G-R relationship is about M_L5.4(M_S5.0)and the M_S4.8 earthquake on August 9 is the largest aftershock of the sequence up to now. With the comparison between the Jiuzhaigou earthquake sequence and the other sequences with the magnitude about M_S7.0 near the field since 1970, we find that there are many apparent differences between the Jiuzhaigou sequence and the two M_S7.2 earthquakes near the Songpan-Pingwu area in 1976 in the spatial position of the aftershocks, the seismogenic structure and the focal mechanism of the mainshocks. Therefore, the conditions were not sufficient for the Jiuzhaigou earthquake to develop into a multiple mainshock sequence. The apparent stress of the mainshock of the Jiuzhaigou sequence is 0.36~0.38MPa. It shows that the earthquake belongs to the undershoot model. The average apparent stresses of the aftershocks are close to the background average stresses of the moderate and minor earthquakes near the Longmenshan fault zone.