Abstract: Based of the data of the seismic catalogue;of the east of China, the author has plotted an evolution curare of the monthly frequency of earthquakes which occurred in Shanxi seismic belt from 1973 to 1983.The corresponding relationship between the curare and the moderate strong earthquakes in North China has been discussed.The results have showed that the Shanxi seismic belt can be considered as a seismicity precursor zone for predicting the coming moderate strong earthquakes in North China.