An experimental study was carried out on the sorption of tetravalent ions Zr4+ and Hf4+ onto hydrous ferric oxide (HFO) and their fractionation behavior during colloid/solution interaction. The sorption of the isovalent ions Zr4+ and Hf4+ onto HFO is nonlinear, and they are fractionated during the sorption and co-precipitation processes: Zr4+ is more affinitive for HFO than Hf4+. At pH<6, the Zr/Hf ratios in solid phase decrease sharply with increasing pH values, but keep unchanged at pH>6. In both cases, the sorption/desorption or particle/water reaction can significantly fractionate Zr/Hf in the surface environment of the Earth.