The invention discloses a method for preparing high-purity cadmium telluride. The reaction process is carried out in a closed quartz tube with melting point above cadmium and tellurium and after carbon coating treatment, wherein the mass ratio of a 5N cadmium material to a 5N tellurium material is 1: 1.1-1.15. The method comprises the following steps: dividing the weighed tellurium material into N parts according to the charging times N, dividing the weighed cadmium material into N-1 parts, alternately adding each part of tellurium material and each part of cadmium material into the quartz tube and adding the tellurium material into the quartz tube firstly and lastly, removing oxygen after charging, sintering and sealing the tube by using a sealed bulb, and slowly performing high-temperature and high-pressure synthetic reaction. The method has the advantages that the contact area of the raw materials is larger in a molten state, the reaction speed is more sufficient compared with the solid raw material, the micro-sized crushing treatment for the raw materials is avoided, the shape requirement of the raw materials is relaxed, the preparation cost is greatly reduced, the purity of the raw material is ensured, the method is suitable for large-scale production, the synthetic conversion rate of the cadmium telluride can reach 98 to 99.5 percent, and the single-tube yield of 800 to 1,000 grams can be ensured by using the quartz tube with the inside diameter of 32 millimeters under the premise of safety.