Abstract: The reactive aggregates are used more and more in water conservancy and hydropower engineering construction in China. For ensuring the safety and the economy of the projects, reasonable and reliable measures are needed to inhibit alkali-aggregate reaction. Derived from specific surface area and synthesized chemical composition, the Physical-Chemical Index of fly ash, which is the mostly used mineral admixtures to suppress ASR, is presented to evaluate the character of fly ash and is applied to integrally reflect the influence of the chemical, mineral and physical properties of fly ash on the suppressing effect of ASR. Hydraulic concrete already has some self-immunity to the ASR. On one hand, reactive stone powder contained in artificial sand disperses the concentrated stress of ASR, and on the other hand, air bubbles entrained by air-entraining agent can supply space to accommodate the products of ASR. The accelerated mortar bar test method overestimates the inhibition effect of fly ash on ASR. Because the mix proportion and the aggregate size of concrete prism are much different from practical hydraulic concrete, concrete prism test method also can not truly reflect the effect of suppressing measures. Considering the special characteristics of hydraulic concrete, such as bigger aggregate size, lower cementitious material content and higher W/C ratio, a new test method for evaluating the suppressing effect of ASR needs to be developed.