CdSe quantum dots (QDs) were synthesized using diphenylcarbazide (DL) to sequester QDs precursors (Cd2+) in situ. Fluorescence (FL) analysis showed the successive synthesis of QDs could be realized by capping with DL and the binding between DL and Cd2+. The average QDs particle size was about 5-20 nm by high-resolution transmission electron microscopy (HRTEM). Fourier transform infrared (FT-IR) spectra showed that CdSe QDs could be chemically bonded with DL. The formation of QDs-DL-Cr(VI) could lower the fluorescence intensity of QDs. In a certain concentration range, the fluorescence intensity and Cr(VI) concentration presented a linear relationship. As a result, this phenomenon could be used to determine the Cr(VI) concentration in the range of 0-24 ×10−6 mol· L−1.