Abstract: Under the long- term complex natural condition and the effect of various both inner and outside forces, earth- rock damis changing momentarily and safety trouble may generate without obvious prewarnings. Especially, because of careless design, poorquality construction and unsuitable management, security of earth- rock dams built earlier encountered many problems. This article, taking Zhengjiachong reservoir dam in Huanggang city, Hubei province as an example, stated overall checkup an appraisal on the safety condition of the reservoir fromthe main aspects, such as engineering geology map, flood- control standard, operation management, project quality, problems in seepage and structure safety, and it made a detail analysis and demonstration on the structural and seepage stability of the dam.