The solid–liquid phase equilibrium for the ternary system of (−)-Shikimic acid + (−)-Quinic acid + H2O and the quaternary system of (−)-Shikimic acid + (−)-Quinic acid + Ethanol (φ ∼ 50%,φ ∼ 75%) + H2O was measured at T = 298.15, 318.15, 333.15, 348.15 K, and mutual solubility was obtained. Three variable-temperature phase diagrams were constructed according to the experimental solubility. In the phase diagrams, there were in all one invariant point, two univariant curves, and two crystallization regions corresponding to (−)-Shikimic acid and (−)-Quinic acid at each temperature in the studied system. The crystallization regions of the pure two solids increase with a decrease in temperature. The variable-temperature diagrams for the quaternary system of (−)-Shikimic acid + (−)-Quinic acid + Ethanol (φ ∼ 50%) + H2O can be used for effective separation and purification of (−)-Shikimic acid and (−)-Quinic acid. Meanwhile, the solid + liquid phase equilibrium data can be used for the separation process of (−)-Shikimic acid and (−)-Quinic acid in industrial production and further theoretical studies.