The invention discloses a high-temperature-resistant saturated brine drilling fluid and a preparation method thereof. The drilling fluid contains 100 parts by weight of water, 2-5 parts by weight of salt resistant soil, 1-3 parts by weight of sepiolite, 10-15 parts by weight of a high temperature and salt resistant fluid loss agent, 1-2 parts of a high temperature and salt resistant diluent, 0.5-2 parts by weight of a high temperature resistant stabilizer, and 35 parts by weight of sodium chloride. The preparation method of the drilling fluid comprises the following steps: respectively adding the salt resistant oil and sepiolite to water, stirring for 20min, ageing for 24h, sequentially adding the high temperature and salt resistant fluid loss agent, the high temperature and salt resistant diluent, the high temperature resistant stabilizer and sodium chloride, and stirring under a speed of 8000r/min to obtain the drilling fluid. The materials of the drilling fluid are convenient to use, can be directly mixed with water, and is stirred for drilling. The drilling fluid has the advantages of good rheological property, strong inhibition performance, realization of the salt resistance saturation in the high temperature environment, realization of the HTHP fluid loss of below 35mL, and benefiting for the hole wall stability and the drill safety.