Data from the expermient on arsenic adsorption by three variable charge soils show that As(Ⅲ) adsorption in creased with pH rising from 3 to 7,and the three soils followed the order: latosol > yellow soil > red soil.While,As(Ⅴ) adsorption decreased with rising pH in red soil and latoso,an opposite trend was observed in yellow soil,making the three soils in the order: yellow soil > latosol > red soil in As(Ⅴ) adsorption.These soils have greater adsorption capacity for As(Ⅴ) than for As(Ⅲ),and the adsorption of either As(Ⅴ) or As(Ⅲ) was related not only to content of the free iron oxides in the soils,but also to crystalline type of the oxides in the soils.The yellow soil showed larger adsorption capacity for As(Ⅴ) than latosol and red soil due to its high proportion of hyd rated iron oxides.Results from the binary system of As(Ⅲ) and As(Ⅴ) indicated that the two species of arsenic competed with each other for adsorption sites on variable charge soils; and As(Ⅴ) was more competitive than As (Ⅲ) under acidic condition,because the presence of As(Ⅴ) depressed the adsorption of As(Ⅲ) to a larger extent,and vice versa in red soil and latosol to a certain extent,but almost noeffect of the presence of As(Ⅲ) on As(Ⅴ) adsorption by yellow soilw as observed except with a high pH.