The invention relates to a liquid-metal thermal interface material with a self-packaging function and a preparation method thereof, and belongs to the technical field of thermal interface materials. In the thermal interface material, liquid metal accounts for 70 vol%-99 vol%; and high thermal conductivity filler accounts for 1 vol%-30 vol%. The liquid metal is formed by mixing two or more kinds of liquid metal with different melting points. The preparation method comprises the following steps that raw materials are cleaned, mixed, and then put into an ultrasonic processor, deionized water is added, ultrasonic treatment is carried out, and then filtering and drying are carried out; and then, the mixture is subjected to hot-pressing into a sheet shape, and finish rolling is carried out to obtain the sheet-shaped thermal interface material. According to the liquid-metal thermal interface material, at a use temperature, the high-melting-point part is in a solid state, the low-melting-point part is in a liquid state, the solid-phase part limits flowing of the liquid phase, the self-packaging effect is achieved, and the liquid-metal thermal interface material has a state of softening paraffin and has high flexibility and no fluidity. In addition, the liquid-metal thermal interface material has a high thermal conductivity (greater than 60 W / mK) and good processability. 60 W / mK) and good processability.