Preliminary conductometric study of interaction between 7-hydroxy-3-(2-methyl-2,3dihydrobenzo[d]thiazol-2-yl)-2H-chromen-2-one (L) and some common cations in acetonitrile solution was shown a selective complexation between L and copper ions in comparison with other metal ions. Thus, L was used as a good sensing material in copper nano-composite carbon paste sensor. Nanocomposite paste contained multi-walled carbon nanotubes (MWCNTs), nano-silica, and ionic liquids which they used for obtain a better sensor response. The proposed potentiometric sensor showed a stable potential response to Cu 2+ ions with Nernstian slope of 29.6±0.3 mV decade -1 over a wide linear concentration range of 7.9×10 -7 -1×10 -1 mol L -1 . The sensor was found to have a short response time of 13 s and to have an acceptable life time of about two months. The application of the sensor to the analysis of copper in waste water samples lead to acceptable results.