Abstract: Facile refluxing or hydrothermal methods were used and bioactive molecule N-acetyl-L-cysteine (NAC) was employed as the ligand to synthesize water-soluble CdTe quantum dots (CdTe QDs) with strong and widely tunable fluorescence emission.Their optical properties were measured with UV-vis spectrophotometer and spectrofluorometer.In addition，the morphology and structure of QDs were further characterized by TEM and XRD.By using NAC as the stabilizer，high-quality aqueous Zn_1-xCd_xSe and CdTe QDs were successfully synthesized with the quantum yields (QYs) reach of up to 62.4%.XRD analysis indicated that the fluorescent emission peaks of QDs were related to their sizes.Using NAC as the ligand，the resulting water-soluble quantum dots were highly fluorescent with the novel property that their fluorescent emission peaks were tunable from 415 nm to 800 nm，i.e.，in the violet-near-infrared (spectral range.The as-prepared QDs exhibited high photoluminescence quantum yields，narrow full-width at half-maximum and high photostability.