Abstract: The water-soluble 3-mercaptopropionic acid(MPA)-stabilized CdTe(MPA-CdTe)quantum dots(QDs)were synthesized by aqueous suspension. The study showed that the fluorescence quenching process of Cu²⁺ to MPA-CdTe QDs, whose largest emission peak was 599 nm, could be described well by the theory of fluorescence quenching in competitive absorption systems and its modification of Stern-Volmer equations. By fittings, the results showed a good polynomial relationship between the fluorescence intensity F0/F and the concentration of Cu²⁺, when the concentration was in the range of 2. 28×10^-6-18. 24×10^-6 mol/L and 4. 8×10^-7-12×10^-7mol/L, and two polynomial equations were respectively elucidated based on dynamic and static quenching in competitive-absorption systems: F0/F=7. 999-2. 470c +0. 339 c², F0/F=3. 154-0. 160 c+0. 049 c² and degree of fitting are 0. 991 and 0. 993, respectively. The detection limit was 1. 326×10^-7.