The interaction between mercaptoacetic acid (MA)-capped CdTe QDs, MA-capped CdTe/ZnS QDs or glutathione (GSH)-capped CdTe QDs with As(III) was studied using fluorescence spectrometry. As (III) has a high-affinity to reduced-GSH to form As(SG)3, and the emission of the GSH-capped CdTe QDs (λem. = 612 nm) is quenched effectively. Thus, a novel fluorescence spectrometric method was developed for As (III) determination by using GSH-CdTe QDs. Under optimal conditions, the quenched fluorescence intensity (F0/F) increased linearly with the concentration of As (III) ranging from 5.0 × 10−6 to 25 × 10−5 mol L−1. The limit of detection (3σ) for As (III) was found to be 2 × 10−8 mol L−1. This method is potentially useful in visual detection of As (III) under irradiation of the ultraviolet light.