A quantificational relationship between carbonization depth and fly ash content as well as carbonation age to the mortars corresponding to five typical concrete mixture ratio of dam interior，exterior and foundation was educed by means of accelerating carbonation test and plurality regression means. The experimental results demonstrated that the carbonation restraint capability of the concrete was degreased with the increase of the fly ash content. The studies on the Ca(OH)2 content of the fly ash-cement paste attested that the replacement of fly ash to cement should be low to 40% in dam exterior concrete according to the results of theoretics calculation, glycerine-ethanol and XRD measurement. The extent of the Pozzloan reaction of the fly ash was reduced with the increase of the fly ash content according to the Ca(OH)2 quantity expended by the Pozzolan reaction resulted from the TG-DTA measurement. The Pozzloan reaction of the fly ash occurred mainly before 90d of the curing age, and it would not be high form 90d till to one year. The fly ash content of the dam interior and foundation concrete may be enhanced to 55% because the dam interior and foundation concrete were not contacted with the atmosphere and the carbonation extent may be very low.