Abstract: Based on experimental study of long term mechanica l characteristics of flexible concrete, it is known that ages have a notable eff ect on mechanical property.For whatever uniaxial compression test or triaxial co mpression test, compressive strength and initial elastic modulus notably increas e with ages, and the ratio of modulus to strength has a decreasing tendency when the age is long. Approximate quantitative relations between mechanical index an d age and confining pressure are obtained by triaxial compression test. Through computing stress and displacement of phase-Ⅱcofferdam in Three Gorges by use o f Duncan-Chang E-μ model, it is known that the safe degree increases with ages.