Abstract: Precursory data of underground fluid before 11 M_S7.0 strong earthquakes since 1969 in China's continent were analyzed in this article. Spatial-temporal characteristics of precursory anomaly of underground fluid before M_S7.0 strong earthquakes were described by using radar and statistical diagram. The result indicates that: ① The anomalies show periodical characteristics and ununiformity in time. The mid-long-term anomalies are dispersing, short-term and impending anomalies are relatively concentrated, each anomaly roughly accounts for 50%. ② The anomalies are concentrated in a certain area and distributed along the active faults. ③ The mid-long-term anomalies appear around the earthquake source region in the earliest stage and show the process of diffusion-concentration-diffusion-concentration, and especially when enter the short-impending stage this concentrating trend becomes more apparent. ④ The percentage of the anomalies in the earthquake source region is larger than that far from the earthquake source region. That is to say: There is a trend that the percentage of the anomalies gets more and more small when the distance is farther from the earthquake source region.

Key words: M_S7.0 strong earthquake, Ground fluid, Precursor anomaly, Earthquake source region, Radar diagram