A method that using potassium permanganate for visual detection of copper ion as indicator established and the reaction mechanism was discussed. The best condition for the determination of copper ion was studied. The results show that the copper ion detection in the range of 5.0×10-8~1.0×10-6 mol/L with the correlation coefficient of 0.998 4 in the BR under pH of 9.62 buffer solution medium. The method has the properties of simple, low detection limit, and wide linear range. It can be used to detect the content of Cu2+in real environmental water samples with satisfactory results.