The stable solid-liquid phase equilibrium for ternary systems of terephthaldialdehyde + 4-hydroxybenzaldehyde + ethyl acetate and terephthaldialdehyde + 4-hydroxybenzaldehyde + acetone was determined using the isothermal saturation method at 293.15, 303.15, and 313.15 K under ambient pressure of 101.2 kPa. In terms of the obtained mutual solubility data, the isothermal phase diagrams of the two systems were constructed. At a given temperature, there were two pure solids formed, pure 4-hydroxybenzaldehyde and pure terephthaldialdehyde, which were identified by Schreinemakers' wet residue method and X-ray powder diffraction analysis. The crystallization zones of pure 4-hydroxybenzaldehyde and pure terephthaldialdehyde increased with rising temperature. The crystalline zone of terephthaldialdehyde was larger than that of 4-hydroxybenzaldehyde at the same temperature. The mutual solubility data of solid-liquid phase equilibrium were correlated with nonrandom two-liquid (NRTL) and Wilson models. The calculated solubility data with NRTL model agreed well with the determined values. The mutual solubility data and ternary phase diagrams for the two systems were of great significance for optimizing the purification procedure of 4-hydroxybenzaldehyde and terephthaldialdehyde.