In this work, nine ternary phase diagrams and three quaternary phase diagrams of different systems at 298.15, 308.15, and 318.15 K were constructed. The ternary solid-liquid phase equilibrium of (uric acid + adenine + water), (uric acid + guanine + water), and (adenine + guanine + water) and quaternary solid-liquid phase equilibrium of (uric acid + adenine + guanine + water were determined at atmospheric pressure (p = 101.3 kPa). The binary solubility of uric acid, adenine, and guanine in water at different temperatures was determined and correlated using the modified Apelblat model, and the mole solubility of adenine was about 30 and 180 times that of uric acid and guanine, respectively. The relative average deviation and root-mean-square deviation values were no more than 1.73 x 10(-2) and 0.102 x 10(-5), respectively. For a ternary system, each phase diagram consisted of one cosaturated point, two cosaturated solubility curves, and three solid-phase regions (two single solid-phase regions and one double solid-phase region). The mutual solubility of uric acid (adenine or guanine) in the systems of (uric acid + adenine + water), (uric acid + guanine + water), or (adenine + guanine + water) increased with increasing temperature. The unsaturated regions enlarged, and the single or double solid-phase regions diminished. For a quaternary system, each Janeck projection of the (uric acid + adenine + guanine + water) system consisted of one cosaturated point, three cosaturated solubility curves, and three solid-phase regions. At the same temperature, the solid-phase regions of three compounds were ranked as guanine > uric acid > adenine. The construction of binary, ternary, and quaternary phase diagrams of uric acid, adenine, and guanine in water was of great significance for studying the deposition of uric acid, and this can also provide reference and basic phase equilibrium data for further study of gout treatment and effects of uric acid on the cardiovascular system.