The solid-liquid phase equilibrium for three systems of succinic acid + urea + water, glutaric acid + urea + water, and adipic acid + urea + water was determined at (288.15 and 303.15) K under atmospheric pressure (0.1 MPa). Six isothermal phase diagrams for these systems were constructed based the measured solubility. The solid-phases were confirmed by Schreinemakers method of wet residue, which corresponded to urea, succinic acid, and 2:1 urea-succinic acid cocrystal (mole ratio) for the succinic acid + urea + water system; urea, glutaric acid, 1:1 urea-glutaric acid cocrystal (mole ratio), and 2:1 urea-glutaric acid cocrystal (mole ratio) for the glutaric acid + urea + water system; and urea, adipic acid, and 2:1 urea-adipic acid cocrystal (mole ratio) for the adipic acid + urea + water system. The ternary systems of succinic acid + urea + water and adipic acid + urea + water included five crystallization fields, three invariant curves, and two invariant points, respectively. The phase diagram of glutaric acid + urea + water included seven crystallization fields, four invariant curves, and three invariant points at a certain temperature. The crystalline region of 2:1 urea-adipic acid cocrystal, 2:1 urea-glutaric acid cocrystal, or 2:1 urea-succinic acid cocrystal is larger than that of other solids for the three corresponding ternary systems. Furthermore, the densities of equilibrium liquid phase were acquired.