The invention relates to a high-temperature-resistant thermoplastic flame retardant material for an automotive wire and a preparation method thereof. The high-temperature-resistant thermoplastic flame retardant material for the automotive wire comprises the following components in parts by weight: 30-50 parts of high-density polyethylene, 10-40 parts of polypropylene resin, 5-20 parts of polyolefin elastomer, 5-15 parts of master batches which can be chemically crosslinked, 30-65 parts of fire retardant, 0.5-3 parts of first antioxidant and 0.8-2.5 parts of lubricating agent. According to the invention, an improved dynamic crosslinking method is adopted, and minimal polypropylene resin is added, so that softness and abrasion resistance of a material can be met, heat resistance of a product can also be guaranteed, and a thermal overload experiment of the product at 150 DEG C can be met. The preparation method of the high-temperature-resistant thermoplastic flame retardant material is simple in process, easy to operate and low in cost.