Comprehensive weighted information content of seismic precursors is a new method, in which anomaly event is comprehensive estimated by using "seismic prediction exprert system", and considering the reliability, validity, significance and dependence every anomaly is given a weighted count. The comprehensive weighted information contents of seismic precursory since 1977 in Shandong provence are calculated and the information content variation before and after the Heze M_S 5.9 earthquake on Nov. 7, 1983, is analysed.