Abstract: This paper gives a prediction method of BC value of earthquake activity magration rate. Making use of above method, the authors calculate BC value of fourly seven M>=6.0 earthquakes which have taken place in mainland China and its neighboring area. Study results show abvious lower BC value anomaly before large earthquakes. Furthermore, this paper analyses the characteristics of BC value in five different study areas of west China in order to test this method. The authors think the changes of lower BC value anomaly before large earthquake is a very effective earthquake prediction method.