Before the occurrence of M_S7.0 earthquake near Jiuzhaigou county in Sichuan province, the earth resistivity measured in shallow wells at Pingliang seismological station, which is situated approximately 360 km from the epicenter, showed an abnormal trend for a year. The anomalous amplitude of NS and EW measuring channels showed annual variation rates of 1.1% and 0.6%, respectively, which were larger compared with the background value (0.6%~0.4% of the normal annual variation). The anomalous change was analyzed by a joint anomaly verification team comprising the China Earthquake Network Center, Earthquake Administration of Ningxia Hui Autonomous Region, and Earthquake Administration of Gansu Province from June 27 to 29, 2017. The analysis results revealed that change occurs in the resistivity of the underground medium, which is the seismic precursory anomaly. Twenty hours prior to the earthquake, the NS and EW channels showed daily variation rates up to 8.9‰ and 1.5‰, respectively. After the mainshock, the measured value basically returned to the background value. This study has a positive research value in predicting earthquakes.