Nitrogen-doped Carbon Dots (NCDs) exhibiting excitation independent emission properties were synthesized by one-step hydrothermal method with sodium citrate as carbon source and ammonia as nitrogen source. NCDs prepared under optimal conditions were characterized by fluorescence spectrometer, TEM, AFM, XPS, and FTIR. The application of NCDs in Fe3+ detection and fluorescence anti-counterfeiting is also explored. The results showed that the optimal preparation conditions of NCDs were sodium citrate concentration of 0.1 mol/L, ammonia concentration of 1.8 mol/L, reaction temperature of 200 ℃, reaction time of 6 h, loading volume of 25 mL. The results demonstrated that the location of fluorescence emission peak of NCDs prepared under the optimal conditions is independent on the wavelength of excitation light, the best excitation wavelength is 343 nm and the best emission wavelength is 443 nm, while the fluorescence quantum yield is 54.9%.In terms of structure, NCDs are spherical with an average particle size of 4.96 nm. The carbon core is graphene-like structure and its surface contains —NH2, —OH and —COOH. The fluorescence of NCDs can be selectively quenched by Fe3+, and the degree of fluorescence quenching ΔF is linear related with the concentration of Fe3+ in the range of 0.1 and 87.5 μmol/L with the limit of detection of 50 nmol/L. In addition, fluorescent ink is prepared with the addition of NCDs, and the pattern printed by the inkjet printer is full as a whole, with clear edge details and strong identification.