The invention discloses a high-temperature-resistant and salt-tolerant spacer fluid with high density and a preparation method of the spacer fluid. The spacer fluid is prepared from solvent water, a suspension stabilizer, a cleaning agent, a fluid loss agent, a retarder, a defoamer, a weighting agent and sodium chloride, wherein the suspension stabilizer is prepared from natural mineral, modified diutan gum, a polymer, inorganic salt and white carbon black; the weighting agent is prepared from iron ore powder and micro-Mn in a weight ratio being 1:(0.05-0.20). The preparation method of the spacer fluid is simple, the suspension stabilizer is added to water slowly, hydration is performed for 5-10 min after high-speed stirring is performed for 1-2 min, then the weighting agent, the fluid loss agent, the cleaning agent and the retarder are added slowly in sequence, the mixed solution is stirred rapidly for 1-2 min, finally, the defoamer is added and uniformly stirred, and preparation is completed. The application temperature range of the high-temperature-resistant and salt-tolerant spacer fluid with high density is 30-190 DEG C, the density is adjustable in a range of 2.00-2.80 g/cm<3>, and the spacer fluid reaches saturation for salt tolerance; the spacer fluid has the advantages of little free water in a system, small fluid loss amount, high fluidity, good slurry stability and the like.