The insoluble species of Gd (Ⅲ) in human blood plasma were investigated by computer simulation. The distribution of the Gd (Ⅲ) species was obtained. It was found that most of the Gd (Ⅲ) ions were bound to phosphate to form precipitate GdPO4 at the concentration of 1. 000 ×10-7 mol/L and when the concentration of the Gd (Ⅲ) increased to 3. 750 × 10-4 mol/L, in excess of the concentration of phosphate, the Gd (Ⅲ) ions were bound to carbonate to form another kind of precipitate, Gd2 (CO3)3.