The invention relates to a method for preparing a thermoelectric compound. The method for preparing a AgSbTe2 thermoelectric material by combining fusant rotatable swinging and discharge plasma sintering is characterized by comprising the following steps of: (1) mixing; weighing thread-shaped Ag, block-shaped Te and granular Sb as initial raw materials according to a chemical formula AgSbTe2+x, wherein x is equal to 0-0.08; (2) preparing mother alloy; mixing the thread-shaped Ag, the block-shaped Te and the granular Sb, placing the mixture into a smelting furnace, heating to 700 DEG C, smelting for 8-10 hours, cooling to 550 DEG C and then quenching in supersaturated saline water to obtain the mother alloy; (3) grinding and tabletting the mother alloy, placing the mother alloy into an induction heating furnace to melt to form a fusant and then rotatably swinging the fusant to obtain a band-shaped product having an amorphous/nanocrystal composite structure; and (4) grinding the band-shaped product having an amorphous/nanocrystal composite structure and carrying out spark plasma sintering to obtain the AgSbTe2 thermoelectric material. The method has short preparation period, low cost, pure phase, simple and easy control of process, safety and no pollution.