In this work, solid-liquid equilibria (SLE) data for the ternary 4-nitro-2-benzofuran-1,3-dione + 5-nitro-2-benzofuran-1,3-dione + 2-propanone system have been measured at (283.15 and 323.15) K respectively. The solid-liquid phase diagrams of the ternary system were constructed based on the measured solubility data. The Schreine-maker's wet residue method was used to confirm the solid phases formed in the system. Furthermore, the density (p) of equilibrium liquid phase was gained. At (283.15 and 323.15) K, two pure solids formed which correspond to 4-nitro-2-benzofuran-1,3-dione and 5-nitro-2-benzofuran-1,3-dione in the ternary 4-nitro-2-benzofuran-1,3-dione + 5-nitro-2-benzofuran-1,3-dione + 2-propanone system.