A preparation method for quantum dots (QDs), comprising following steps: providing initial QD cores, mixing the initial QD cores with an organic carboxylic acid to bond the organic carboxylic acid to a surface of the initial QD cores; preparing a shell layer on the surface of the initial QD cores, wherein the step of preparing the shell layer on the surface of the initial QD cores is performed in a shell-growth reaction system containing an organic carboxylic acid, the source of the organic carboxylic acid in the shell-growth reaction system is the remaining organic carboxylic acid after the step of mixing the initial QD cores with the organic carboxylic acid to bond the organic carboxylic acid to the surface of the initial QD cores; and mixing and heating a solution system, obtained after a completion of shell-layer growth reaction, with an organic amine, or mixing and heating the solution system, obtained after the completion of the shell-layer growth reaction, with an organic phosphine, or mixing and heating the solution system, obtained after the completion of the shell-layer growth reaction, with a mixed solution of an organic amine and an organic phosphine, wherein the shell-growth reaction system is a reaction material system applied in the process of growing a shell layer on the surface of the initial QD cores, the initial QD cores may be at least one selected from group II/VI QD cores, group III/V QD cores, group III/VI QD cores, and group II/III/VI QD cores, and the organic carboxylic acid is one or more selected from organic carboxylic acids having 8 to 18 carbon atoms, the organic amine is one or more selected from organic amines having 8 to 18 carbon atoms, and the organic phosphine is at least one selected from trioctylphosphine and tributylphosphine. providing initial QD cores, mixing the initial QD cores with an organic carboxylic acid to bond the organic carboxylic acid to a surface of the initial QD cores; preparing a shell layer on the surface of the initial QD cores, wherein the step of preparing the shell layer on the surface of the initial QD cores is performed in a shell-growth reaction system containing an organic carboxylic acid, the source of the organic carboxylic acid in the shell-growth reaction system is the remaining organic carboxylic acid after the step of mixing the initial QD cores with the organic carboxylic acid to bond the organic carboxylic acid to the surface of the initial QD cores; and mixing and heating a solution system, obtained after a completion of shell-layer growth reaction, with an organic amine, or mixing and heating the solution system, obtained after the completion of the shell-layer growth reaction, with an organic phosphine, or mixing and heating the solution system, obtained after the completion of the shell-layer growth reaction, with a mixed solution of an organic amine and an organic phosphine, wherein the shell-growth reaction system is a reaction material system applied in the process of growing a shell layer on the surface of the initial QD cores, the initial QD cores may be at least one selected from group II/VI QD cores, group III/V QD cores, group III/VI QD cores, and group II/III/VI QD cores, and the organic carboxylic acid is one or more selected from organic carboxylic acids having 8 to 18 carbon atoms, the organic amine is one or more selected from organic amines having 8 to 18 carbon atoms, and the organic phosphine is at least one selected from trioctylphosphine and tributylphosphine.