We synthesized the water-soluble CdTe quantum dots (CdTe QDs) with longer emission wavelength, constructed the luminol-CdTe QDs chemiluminescence resonance energy transfer (CRET) system, and realized the high selectivity ratio detection for Cu2+. Herein, based on the Irving-William sequence, it was found that the paramagnetic ion Cu2+ generally binds more strongly than the diamagnetic ion Cd2+. When Cu2+ is added to the system, Cu2+ tends to bind to the sulfhydryl group (SH) of stabilizer on CdTe QDs, leading to surface defects of CdTe QDs, which quenches the chemiluminescence (CL) signal remarkably. Meanwhile, due to the superior coordination ability of Cu2+ and ratio detection, the system has better selectivity and anti-interference performance. The method achieved a highly sensitive, selective, yet reliable measurement of Cu2+ in the concentration range of 0.5 × 10-7-20 × 10-7 M, with a low detection limit of 8.4 nM. Importantly, the sensor has been successfully exploited to detect Cu2+ in tap water and lake water.