The invention discloses a preparation method of a polypropylene fiber-glass fiber thermoplastic composite material. The preparation method comprises the following preparation steps of 1 preparing of polypropylene fibers; 2 preparing of glass fibers; 3 mixing of the polypropylene fibers and the glass fibers, wherein the polypropylene fibers and the glass fibers are mixed through a fiber self-weighing mixing system, the humidity of a mixing environment is controlled to be 33% to 43%, and the temperature of the mixing environment is controlled to be 20 DEG C to 30 DEG C; 4 fiber needling felt forming, wherein the precisely-mixed polypropylene fibers and glass fibers are carded with a carding machine and lapped through a clamping type lapping machine to obtain a fiber net, then fiber needling felt forming is conducted through pre-needling equipment and main needling equipment, and lastly cutting and rolling are conducted to obtain the polypropylene fiber-glass fiber thermoplastic composite material. According to the preparation method, the process steps are simple, the production process is continuous, the production efficiency is high, the equipment is simple, and the technology is convenient to master; the polypropylene fiber-glass fiber thermoplastic composite material has the advantages that on one hand, the good heat-conducting property is achieved, on the other hand, the mechanical property of a heat-conducting material is enhanced, and processing is convenient.