The invention relates to the field of heat conduction materials and provides low-melting-point alloy. The low-melting-point alloy comprises, by mass, 47.0-50.8% of indium, 29.5-32.3% of bismuth, 13.5-16.3% of tin and 0.67-10% of gallium. A preparation method of the low-melting-point alloy comprises the steps that A, all the constituents are weighed according to requirements; B, the furnace temperature is increased to 350 DEG C, the bismuth and the tin are placed into a ceramic crucible, the ceramic crucible is placed into a smelting furnace to be heated, after the bismuth and the tin are melted, surface oxide is removed, and stirring is conducted; C, the furnace temperature is adjusted to 200 DEG C, the indium is added, and after the indium is completely melted, surface slagging-off and stirring are conducted; D, the furnace temperature is adjusted to 100 DEG C, the gallium is added, and slagging-off and standing are conducted after stirring; and E, the crucible is taken out, the alloy is poured into a mold, and cooling is conducted. The melting point of the low-melting-point alloy is 40-60 DEG C, the low-melting-point alloy is used for low-junction-temperature occasions in a phase-change mode, and the application space of liquid metal thermal interface materials is enlarged; harmful elements such as lead and cadmium are not contained in the low-melting-point alloy product, and environment protection is facilitated. The preparation method is simple in technological requirement, and the whole process can be conducted in the atmospheric environment.