The expansion behavior of typical siliceous carbonate(Spratt limestone) autoclaved in LiOH solution were studied in this paper, the morphologies and chemical composition of the products produced by reaction of siliceous carbonate with LiOH were studied through SEM and EDS. The results show that Spratt limestone exhibits both alkali-silica and alkali-carbonate reactivity. Ion's migration in alkali-carbonate reaction process was revealed, dolomite crystal disintegrates because of alkali corrosion, Ca~(2+) and CO_3~(2-) produced by dolomite crystal disintegration migrate out and leave original positions.