Abstract: We collected digital geomagnetic data of 102 geomagnetic stations across the country from 2008 to 2015, and calculated the space correlation coefficient between the station geomagnetic total field F on local time 02 by the geomagnetic spatial correlation method. According to the same standard of abnormal judgement, we find that the spatial correlation has obvious anomaly low value before 5 of 17 moderate to strong earthquakes in the studied time period, which respectively are Shanxi-Ningqiang M_S5.1 earthquake on September 19, 2009, Sichuan-Qingchuan M_S5.4 earthquake on November 1, 2011, Liaoning-Dengta M_S5.1 earthquake on January 23, 2013, Gansu-Minxian M_S6.6 earthquake in July 22th, 2013, Jilin-Qianguo M_S5.5 earthquake on October 31, 2013. By summarizing the anomaly characteristics of the 5 earthquake examples, we found that their abnormal features are very similar, and the duration time is about 20 days, then the earthquakes occurred within 3 months after the start of the anomalies. At the same time, the earthquakes occurred near the center of the abnormal clusters, and the size of the anomaly area is about 500 km. Our results accumulate abundant data and material for further analysis of the anomaly characteristics of geomagnetic spatial correlation before earthquakes.

Key words: Geomagnetic total field, Earhquake precursor, Spatial correlation