A simple, sensitive and environmentally friendly method was developed for determination of chemical oxygen demand (COD) by cyclic voltammetry using nickel-copper (NiCu) alloy electrode. The structure and the electrochemical behavior of NiCu alloy electrode were investigated by atomic force microscope, energy dispersive X-ray spectrometer, and cyclic voltammetry, respectively. The results indicated that NiCu alloy film with high quality was stably modified on the surface of glass carbon (GC) electrode, which could effectively oxidize a wide range of organic compounds. Subsequently, the parameters affecting the analytical performance were investigated, including pH, dissolved oxygen and concentration of chloride ion. Under optimized conditions, the linear range was 10-1533 mg L-1 and the detection limit was 1.0 mg L-1. The results obtained from the proposed method were linearly correlated to those by the classic dichromate method (r = 0.9978, p < 0.01. n = 13). Finally, the validated method was used to determine the COD values of surface water, reclaimed water and wastewater. It was shown that the proposed method had an excellent practical perspective on determination of COD in water quality control and pollution evaluation. (C) 2012 Elsevier Ltd. All rights reserved.