Some of the acidic reagents or medicines (i.e. HCl, GSH & GSSG, Vit. C, Vit. B6) and basic reagents (Tris) were used to regulate the pH of water soluble protein and urea soluble protein solution of human lenses. At a certain pH, the lens protein solution appears opalescence, the pH of opacity solution which is measured by pH meter is around 5.6-6.3. The opalescence of water soluble and urea soluble lens protein solution of human fetal, adult and cataractous lenses were also determined by gradient acidic and basic solution. The result show that the opacity is more obvious in soluble protein solution of cataractous lenses and clear lenses than in that of fetal lenses, and the lens urea soluble protein has a marked opalescence in comparison with the water soluble protein. So we assume that cataractogenesis might be associated with the change of pH within lens.