Abstract: The physical properties of iron sorbitol complex has been examined by a variety of techniques including infrared spectroscopy, electron microscopy, ultrafiltration, gel chromatography and osmometry. IR spectroscopy in the region 700～1100 cm^-1 suggested the presence of β-FeOOH. Electron microscopy showed the complex particle to be spherical with a diameter of 15～30 nm. The ultrafiltration and chromatographic experiments on Sephadex G-200 showed the range and the distribution of molecular weight. The molecular weight (Mn)of the complex was found to be 1.7×10⁵ by osmometry. The relationship between intrinsic viscosity and molecular weight for the iron sorbitol complex was shown to be η=3.84×10^-4M^0.47.