A method for preparing cadmium sulfide nanocrystals emitting light at multiple wavelengths. The method comprises the steps of (a) mixing a cadmium precursor and a dispersant in a solvent that weakly coordinates to the cadmium precursor, and heating the mixture to obtain a cadmium precursor solution, (b) dissolving a sulfur precursor in a solvent that weakly coordinates to the sulfur precursor to obtain a sulfur precursor solution, and (c) feeding the sulfur precursor solution to the heated cadmium precursor solution maintained at a high temperature to prepare cadmium sulfide crystals, and growing the cadmium sulfide crystals. Further, cadmium sulfide nanocrystals prepared by the method. The cadmium sulfide nanocrystals have uniform size and shape and can emit light close to white light simultaneously at different wavelengths upon excitation. Due to these characteristics, the cadmium sulfide nanocrystals can be applied to white light-emitting diode devices.