How to apply Hurst exponent of seismic frequency to predicting earthquake in Jiangsu province and its adjacent area is studied. It indicate that the Rvalue derived from retrospective prediction test to the earthquakes (M_S ≥ 5.0)in the area since 1970 is 0.365, and 81.8%of earthquakes which are predicted correctly take place in one year after anomoly start. Therefore it can be used for predicting earthquake in Jiangsu province and its adjacent area.