Abstract: Based on the mixing experiment over six mixing ratio,the geochemical models of the hydrochemical components of the leach after the 0,1,3,7,14 and 21 days are conducted differently.The formation mechanism of the leach hydrochemistry was studied.The results show that the leach of the Baqiao power plant is a high pH solution for the CaO dissolution;the mineral dissolution/precipitation and ion exchange is the main hydrogeochemical reaction in the flyash-water system.