The invention relates to the technical field of lubricating oil, and discloses high-temperature lubricating grease and a preparation method thereof. The lubricating grease is prepared from the following raw materials in parts by weight: 50-70 parts of base oil, 20-30 parts of fatty acid calcium, 10-14 parts of magnesium phosphate, 5-7 parts of liquid paraffin, 5-7 parts of turkey red oil, 16-20 parts of aluminum isopropoxide, 10-12 parts of stearic acid, 8-10 parts of silicone oil, 4-8 parts of nanometer silica powder, 1-3 parts of an antioxidant, 10-18 parts of alkyl phenolic resin, 15-20 parts of phosphate, 10-18 parts of acrylic resin, 18-25 parts of pentaerythritol, 12-18 parts of polyurea, 5-9 parts of trisodium phosphate, 16-24 parts of polyethylene glycol, 4-11 parts of graphite fibers, 3-9 parts of nano molybdenum powder, 5-11 parts of nano cerium oxide powder, 2-8 parts of nano calcium borate, 1-4 parts of sodium antimony gluconate and 1-3 parts of bismuth potassium citrate. According to the preparation method for the high-temperature lubricating grease, the scientific and appropriate components and the reasonable usage amount are combined, so that the prepared lubricatinggrease has the advantages of being stable in quality, excellent in extreme pressure antiwear property, corrosion resistance, oxidation stability and high-temperature resistance and long in service life.