Abstract: Objective: A fluorescence detection method based on copper doped carbon quantum dots(Cu-CDs) was developed for the determination of vanillin in food. Method: Cu-CDs, with stable performance, were prepared by one-step hydrothermal method using ascorbic acid as precursors and copper sulfate as metal dopant. The morphology, elementary composition and optical properties of the synthesized Cu-CDs were characterized by energy dispersive X-ray spectrometers, fourier transform infrared spectroscopy, ultraviolet and fluorescence techniques. The quenching effect of the Cu-CDs with vanillin was further studied. Results: C and Cu were evenly distributed in Cu-CDs solution. The Cu-CDs were rich in functional groups such as amino, carboxyl and hydroxyl groups, indicating that Cu-CDs had good water solubility. It was also found that vanillin had strong fluorescence quenching effect on Cu-CDs in the pH7.0 KH₂PO₄-K₂HPO₄ buffer solution, and the concentration of tetracycline in the range of 1～400 μmol/L showed a good linear relationship with the fluorescence quenching intensity of Cu-CDs, and the linear equation was y=0.0045x+0.1934（R²=0.9917）, the detection limit was 0.33 μmol/L. What’s more, it was applied to the determination of vanillin in food samples, the recovery was 98%~110%. Conclution: The method for the determination of vanillin has the advantages of low cost, high specificity, simple operation, and a good application prospect.