In this study, the solubility of the ternary system (NaH2PO4 + CO(NH2)(2) + H2O) at (308.15, 328,15, and 348.15) K were determined, using isothermal solution saturation The equilibrium solid phases were analyzed by the Schreinemaker's method of wet residues and verified by X-ray diffraction (XRD). According to the experimental data, the phase diagrams were plotted and the crystallization areas were determined. The phase equilibrium at different temperatures were compared and discussed. This research provides an accurate answer for whether crystalline hydrate and urea phosphate exist in this system or not. All results can offer fundamental data for crystallization processes and further theoretical studies.