On October 20, 2016, an earthquake of magnitude 4.4 occurred in Sheyang County, Yancheng City, Jiangsu Province. Before the earthquake, the "double low-points" anomaly in daily variation of vertical geomagnetic component was observed in some magnetic observatories in East China. The period of low points on both sides of the dividing line was more than 2 hours. Some scholars have found that the occurrence of geomagnetic "double low-points" is related to the generation and occurrence of earthquakes.