The invention discloses a preparation method of electropositive water-soluble cadmium telluride quantum dots. The method comprises the following steps: respectively adding an aqueous solution of cadmium chloride and an aqueous solution of aminoethyl mercaptan into an ethanol-water solution, and uniformly mixing to obtain a mixed solution, wherein eh volume percentage of ethanol in the mixed solution is not greater than 50%, and a molar ratio of aminoethyl mercaptan to cadmium chloride is 3-4:1; adjusting the pH value of the mixed solution to 5-6, introducing nitrogen for above 30min, adding an aqueous solution of sodium hydrogen telluride, and uniformly mixing to obtain a cadmium telluride precursor solution, wherein a molar ratio of sodium hydrogen telluride to cadmium chloride is 0.1-0.2:1; and heating the cadmium telluride precursor solution at 70-100DEG C to obtain the electropositive water-soluble cadmium telluride quantum dots. The electropositive water-soluble cadmium telluride quantum dots with high fluorescence quality can be obtained by utilizing the method, and the highest fluorescence quantum yield reaches 31%. The electropositive water-soluble cadmium telluride quantum dots obtained in the invention have a good crystal lattice structure.