In this article, the blue luminescent carbon quantum dots (CQDs) were prepared by hydrothermal method using pyrolysis of gelatin. The temperature, time of the prepared CQDs were optimized via single-factor experiments to select the optimal conditions for the preparation of CQDs. The results showed that fluorescence of carbon quantum dots was the strongest when the carbonization temperature was 200 ℃, and time was 6 h. At the same time, the obtained carbon quantum dots under the optimal conditions was characterized by transmission electron microscope (TEM), UV-visible spectroscopy, photoluminescence spectroscopy (PL), fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD), the result indicating that the quantum yield of carbon quantum dots prepared by this method is 39.4%, and the quantum yield is relatively higher than that of carbon quantum dots that do not doped, which may be due to the presence of N elements that increase the quantum yield, and the prepared carbon quantum dots not only have rich oxygen-containing functional groups but also have good photobleaching performance, and the morphology of the carbon quantum dots is mainly spherical with uniform dispersion and no obvious lattice fringes, which is consistent with the morphology of the carbon quantum dots reported in related literatures; And the carbon quantum dots had weak absorption at 250~300 nm, but there was no obvious characteristic absorption peak, which may be due to the n—π* transition of the CO group; In addition, the pH, the Xenon lamp irradiation time, the concentration of carbon quantum dots, the type of solvent, andionic strengthon the fluorescence properties of carbon quantum dots were discussed. The results showed that the irradiation time of the xenon lamp and ionic strength had little effect on the fluorescence performance of the carbon quantum dots. The fluorescence intensity is relatively weak under peracid or overbase conditions, which may be due to protonated or non-protonated effects resulting in decreased fluorescence intensity under peracid or overbase conditions. And as the concentration of the carbon quantum dots increased, the fluorescence intensity increased first and then decreased. For the solvent type, the fluorescence intensity in the polar solvent was greater than the fluorescence intensity in the non-polar solvent which indicated that the carbon quantum dots had good water solubility by this method.