Carbon quantum dots（CDs） with green fluorescence were synthesized by nitric acid oxidation and hydrothermal method with Taixi coal as carbon source.The CDs had good stability and water dispersibility with an average diameter of 3.64 nm.The structures and optical properties of the CDs were characterized by transmission electron microscopy（TEM）,X-ray photoelectron spectroscopy（XPS）,Fourier transform infrared spectroscopy（FTIR）,UV-Vis spectroscopy and fluorescence spectroscopy.Based on the fluorescence quenching principle,the fluorescence intensity of CDs decreased with the increase of Fe3+ concentration under the optimal detection conditions.The fluorescence quenching efficiency of CDs was in good linearity with Fe3+ in the concentration ranges of 0.6×10-6-2.5×10-6 mol/L and 3.0×10-6-21.0×10-6 mol/L,and the detection limit for Fe3+ was 6.7×10-7 mol/L.