Abstract: In this parper, a sort of new rare earth color reagent-polyhalogenated bisazo chromotropic acid derivcnts have been designed and synthesized. They are easily soluble in water, alcohol and acelone, but insoluble in benzene, ether and chloroform. The absorption maxima of arscnazo or carboxyazo types reagents are at about 527-540nm and chlorophosphonoazo type at 543-549nm. The absorption maxima of the complexes of reagents with rare earth elements are at 628-650nm.The color reagents can react with rare earth elements not only in weak acidic medium (pH = 2-5), but also in strong acidic solution (such as 0.1-4N HCl, H₂SO₄, HClO₄ and H₅PO₄).