A simple，rapid and mild condition method was developed for the preparation of ZnO@SiO2 core-shell structures quantum dots and Ag@SiO2/ZnO@SiO2 nanocomposite.Particle sizes，UV-vis absorption and emission spectra were characterized by transmission electron microscopy（TEM），ultraviolet spectrometry（UV），fluorescence spectroscopy（FL），nanometer particle size analyzer and ZETA potentials techniques.The results showed that the particles sizes of ZnO@SiO2 core-shell structures quantum dots were 3-8 nm and could emit yellow green fluorescence under the excitation of UV-vis light.Their maximum absorption wavelength was 330 nm，and the maximum fluorescence emission wavelengths were located at 510 nm.Ag@SiO2/ZnO@SiO2 could enhance the fluorescent of ZnO@SiO2 core-shell quantum dot，but it didn-t - change the emission peak position of ZnO@SiO2 core-shell quantum dot.Otherwise，Ag@SiO2/ZnO@SiO2 greatly enhanced the fluorescent stability of ZnO@SiO2 core-shell quantum dots at room temperature.Based on different level quenching of hemoglobin and L-cysteine for quantum dots,a simple，rapid and sensitive detection method was established.Under the optimized conditions，the characteristic fluorescence intensity of Ag@SiO2/ZnO@SiO2 at 510 nm was linearly proportional to the concentration of L-cysteine and hemoglobin in ranges of 0.068-10.10 mg/L and 4.00×102-4.00×103 mg/L，respectively.The detection limits were 6.92×10-3 mg/L and 2.04 mg/L，respectively，and the correlation coefficients were 0.993 8 and 0.995 1,respectively.The relative standard deviations for 11 replicate detections of 3.37 mg/L L-cysteine and 2.00×103 mg/L hemoglobin were 1.3% and 2.5%，respectively.