Taking a region with high arsenic polluted groundwater in Datong Basin as the research object, the migration and transformation of Fe(Ⅲ)in underground-sandy aquifer were studied through an indoor dynamic simulation experiment. The results showed that migration and transformation behaviors of Fe(Ⅲ)in underground-sandy aquifer match the first order migration reaction kinetics with a increasing rate constant. In the beginning of the experiment, Fe(Ⅱ)was the primary component in effluent, and Fe(Ⅱ)content reached to the highest value after 300 hours. Then, after the oxygen gradually entered the sand column, Fe(Ⅱ)was oxidized to Fe(Ⅲ). When the iron reached its balance in underground-sandy aquifer, the total adsorption of Fe was 0. 4195mol, which was equivalent to the adsorption concentration of Fe ions by sand was0. 3648 mol/kg. The Fe ion concentration in water was 3. 929 mmol/L, and the value of K_d was 0. 0928 L/kg. Deposition reaction kinetics results showed that the cumulative deposition of FeCl₃ in sand was 2. 469 g, and the deposition rate was 50. 01%. The average deposition rate was 0. 015 g per number of pore volume. During the transformation of iron in underground-sandy aquifer, the sedimentation was very obvious besides the convection-dispersion effect.