Abstract: The extract solution was obtained by ultrasonic crushing with using larch bark as raw material and 40% ethanol aqueous solution as solvent, and ethylenediamine was then added to prepare N-doped carbon dots(NCDs) by hydrothermal synthesis method. FT-IR, XPS, TEM, XRD and UV were applied to characterize and analyze the structure of NCDs. The results showed that the prepared NCDs mainly contained three elements of C, N and O, and the surface bear benzene ring, amino, hydroxyl and carbonyl groups. The NCDs were spherical particles with an average particle size of 4.8 nm, and had (002) lattice plane of graphitized carbon core. The existences of ultraviolet absorption caused by π-π^* and n-π^* electron transitions was in the region of ≤300 nm and 300-600 nm. These results confirmed that NCDs were mainly composed of graphitized carbon core and surface functional groups. In addition, fluorescence analysis showed that NCDs had excitation dependence and stability against photobleaching, and the fluorescence intensity decreased with increasing temperature. The analysis of the effect of different metal ions on the fluorescence intensity of NCDs showed that Fe³⁺ had selective fluorescence static quenching effect on NCDs with the limit of detection(LOD) of 9.07 μmol/L. Additionally, the yellow-green phosphor NCDs/SiO₂ was also prepared by the composite method and was used as the color conversion layer. The white light-emitting diodes(WLEDs) with CIE color coordinates of (0.318 2, 0.303 0), correlation color temperature of 6 381 K and color rendering index of 84.1, were obtained by using blue emission(450 nm) semiconductor chip encapsulation.