The invention discloses a method using a water-soluble cadmium telluride quantum dot as a light-emitting layer to build a water-soluble quantum dot LED. The method comprises the steps that the film layer of ITO conductive glass is etched into strips; ultrasonic cleaning, removing out and drying are carried out; a PEDOT:PSS solution is spin-coated on the ITO conductive glass, and annealing is carried out; PVK is dissolved in toluene to form a solution and is spin-coated on a PEDO:PSS layer, and annealing is carried out; a water-soluble cadmium telluride solution is spin-coated on a PVK layer, and annealing is carried out; Alq3 is dissolved in ethanol and is spin-coated on a water-soluble cadmium telluride quantum dot layer, and annealing is carried out; and aluminizing is carried out on the Alq3 layer in a heat evaporation manner and in the manner of crosswise intersecting with the etched ITO film layer. According to the invention, the quantum dot LED is built based on the water-soluble cadmium telluride quantum dot; the electroluminescent property of the water-soluble quantum dot is verified; and the building method of the water-soluble cadmium telluride quantum dot LED is provided for the first time.