The invention relates to an amorphous tellurium-cadmium-mercury/crystalline silicon heterojunction infrared-detector, which is characterized by being composed of a crystalline silicon substrate, amorphous tellurium-cadmium-mercury, a first metal electrode and a second metal electrode, wherein the amorphous tellurium-cadmium-mercury and the crystalline silicon substrate form heterojunction, the first metal electrode is connected with the amorphous tellurium-cadmium-mercury, and the second metal electrode is connected with the crystalline silicon substrate. The preparation process comprises the following steps of substrate cleaning, amorphous tellurium-cadmium-mercury film preparation, photosensitive surface forming, metal electrode preparation and package test; or substrate cleaning, second metal electrode preparation, amorphous tellurium-cadmium-mercury film preparation, photosensitive surface forming, first metal electrode preparation and package test. The amorphous semiconductor material has no selectivity for the substrate, the lattice matching performance between materials forming heterojunction is better, and the significant photoelectric response exists. The optimum working temperature of the detector is close to room temperature, two stages of semiconductors are utilized for refrigeration, and the weight, the power consumption and the manufacturing cost of the infrared detector assembly are reduced.