The invention provides a method for synthesizing a ZnCdS/ZnS core-shell-structured nanocrystal with good ianthinus fluorescence in a one kettle way, with common cadmium salt and zinc salt used as precursors for cadmium and zinc. The method is the most economic and environment-friendly method for synthesis of high-quality ZnCdS/ZnS core-shell-structured nanocrystals at present. The method has the advantages of simple synthesis process, good repeatability, safety, environment friendliness, no need for a glove box and capacity of saving more than 60% of cost. The fluorescence of the synthesized ZnCdS/ZnS core-shell-structured nanocrystal is continuously adjustable in a range of 400 to 490 nm. The nanocrystal has uniformly distributed particle sizes, high fluorescence quantum yield (50 to 100%) and narrow half height. More important, the method is applicable to large-scale synthesis of high-quality nanocrystals, so the method has an immense application value in both laboratory synthesis and industrial synthesis.