In the paper,we statistically analyze the sudden impending earthquake anomalies and obvious trend anomalies of all kinds of precursors of 11 great earthquakes(Bohai Ms7.4,Luhuo Ms7.9,Yongshan Ms7.1 ,Haicheng Ms7.3,Longling Ms7.4,Tangshan Ms7.8,Songpan Ms7.2,Daofu Ms6.9 Wuqia Ms7.4,Lancang Ms7.6,Gonghe Ms7. 0)in Chinese continent from 1969 to l990 by synthesizing many stages and phenomena. Then we study the whole characters and physical explaination of sudden anomalies before the megaseisoms,summarize the ev...