Effects of removing organic matter with hydrogen peroxide, adding 1% humic acid, and removing free Fe-Al oxides with DCB (dithionite-citrate-bicarbonate) on adsorption of oxalic, citric, tartaric and malic acids by red soil developed from red clay were studied with the batch equilibrium method. Results show that due to the possible change of solution pH, surface sites, soil structure, activity of surface group, and the formation of oxalate, removal of organic matter slightly increased adsorption amount of low molecular weight organic acids, but the increase was not obvious; due to the possible change of surface charge, the cover of surface sites, the activity of Fe oxides, and the protonation of groups, addition of humic acid slightly decreased the adsorption amount after one month incubation, but the reduction was also not obvious; and the adsorption amount was reduced significantly in the soil with 3.79% of the free Fe-Al oxides removed because of the significant decrease of positive charge, and the reduction of adsorption amount varied with the kind of organic acids, showing an order in reverse to that of the original soil in terms of maximum adsorption of organic acids.