Abstract <p>The Phycoerythrin-Nitrocellulose test paper (PNTP) for the content of copper ions in water is prepared by loading the Phycoerythrin on activating nitrocellulose membrane, which can be used on the test of wastewater. Its detection ability is explored under different pH values and various additional metal ions through the colorimetry. The optimal conditions of PNTP preparation have been determined to be the material/liquid ratio of 1 : 1 and PE concentration of 0.04 mg/mL, respectively. Meanwhile, its specificity for detection copper ions has been proved by our experiments. Our experimental results show that the detection accuracy of copper ions reaches 10 mg/L at pH 3 and 4, 0.01 mg/L at pH 5 and 7, and 0.1 mg/L at pH 6 and 8. This meets the requirements of most water quality monitoring and is suitable for on- site rapid detection of copper ion concentration in water.</p>