Abstract: The preliminary accelerated mortar-bar test showed that the aggregate has potential alkali activity hazards in intake complex of CCS hydropower station in Ecuador. Used volcanic ash and volcanic ash+silica fume as admixture to inhibit the alkali activity of aggregate. The results show that adding volcanic ash or volcanic ash+silica fume has a significant inhibition effect on the alkali reaction, and with the amount increasing, the expansion rate of the mortar-bar specimen has a significant decrease trend; while the sample expansion ratio of volcanic ash+silica fume is smaller than volcanic ash, so using volcanic ash+silica fume as admixture has better inhibition effect on alkali activity. This research enabled the project to use local materials as concrete aggregates in the construction process, saved engineering investment and shortened construction period; at the same time, it provided valuable experience for overseas engineering survey design and construction.