The cadmium telluride (CdTe) quantum dot with good water solubility, narrow peak width at half height and uniform particle dispersion was synthesized in alkaline medium using mercaptopropionic acid (MPA) as stabilizing agent. In presence of dithizone, the recovering extent of CdTe quantum dot fluorescence intensity was in direct proportion to the concentration of lead ions. Based on this phenomenon, a new determination method of lead ion by CdTe quantum dot fluorescence switch was established. To colorimetric tube were added into 1 mL of 2.5×10^-4 mol/L CdTe quantum dot solution (in Cd²⁺), proper amount of borate buffer solution at pH 10.0 and 1 mL of 90 μmol/L dithizone ethanol solution. After complete reaction for 5 min, the Pb²⁺ standard solution with different concentration gradients was added. After diluting the solution to 5 mL with borate buffer solution at pH 10.0 and placing for 5 min, the relative fluorescence intensity of testing system was measured at 400 nm/600 nm for excitation wavelength/ fluorescence emission wavelength (λ_ex/λ_em). It was found that the concentration of lead ion in range of 2.0×10^-6 - 9.0×10^-5 mol/L showed good linearity to the corresponding relative fluorescence intensity. The correlation coefficient was r=0.997 6, and the detection limit of method was 3.3×10^-7 mol/L. The proposed method was applied to the determination of lead in soil and lake water samples, and the found results were consistent with those obtained by atomic absorption spectrometry (AAS). The relative standard deviations (RSD, n=6) were between 0.99% and 1.0%, and the recoveries were between 95% and 105%.