Abstract: AntipyrylazoⅢ,or in its systematic nonmenclature 3,6-bis-(4-antipyrinylazo)-4,5-dihydroxynaphthalene-2,7-disulfonic acid,was synthesized,and optimum conditions for its chromogenic reaction with Cu(Ⅱ) ion were studied. In a borate buffer medium of pH 10.0-11.5 a coordination complex was formed between antipyrylazoⅢ and Cu(Ⅱ) ion with mole ratio of 1 to 1. Its absorption maxima was found at the wavelength of 590 nm,where the molar absorptivity was 5.1×104L·mol-1·cm-1. Linear relationship between the absorbance of the coordination complex and the concentration of Cu(Ⅱ) ion was obtained in the range within 50 μg/25 mL of Cu(Ⅱ). The proposed method has been applied to the determination of copper in samples of copper ore and aluminum alloy.