Abstract: In this paper, the MYCIN inexact inference method in Expert System is applied to earthquake comprehensive prediction, and it is proposed that the methods of determining various certainty factors, correcting correlation between anomalous evidences and computing the comprehensive certainty factor of occurrence of some moderate or strong earthquake. By use of the method the 18 earthquake cases since 1966 in North China are tested with the seismologic anomalies, and the comprehensive certainty factors of occurrence of some moderate or strong earthquake are computed. Finally some problems in the application are discussed.