The invention discloses a long-acting low-temperature phase-change cool-storage material, and a preparation method thereof. The long-acting low-temperature phase-change cool-storage material is composed of, by weight, 10 to 15% of ammonium chloride, 5 to 10% of sodium nitrate, 1 to 5% of sodium phosphate, 10 to 20% of n-dodecane, 10 to 15% of n-decane, 5 to 10% of a surfactant, and the balance water. The preparation method comprises following steps: (a) ammonium chloride, sodium nitrate, and sodium phosphate are dissolved in water, and an obtain mixture liquid is stirred so as to realize complete dissolving; (b) n-dodecane, n-decane, and the surfactant are mixed, and an obtained mixed solution is stirred to be uniform; (c) the mixture liquid is mixed with the mixed solution, and an obtained product is stirred to be uniform. Solidification temperature of the long-acting low-temperature phase-change cool-storage material ranges from -30 to -12 DEG C, phase change latent heat ranges from 300 to 340J/g, and long-term refrigeration can be realized.