Liquid-liquid equilibria of three ternary systems-methanol-heptane-1,3-dioxolane, methanol-heptane-1,4-dioxane, and methanol-heptane-terahydropyran-were measured at 253.15, 273.15, 283.15, 293.15 and 303,15K for the first and third systems, and at 273.15, 283.15, 293.15 and 303.15K for the second system, 1,3-dioxolane, 1,4-dioxane and tetrahydropyran are cyclic ether compounds. We found expanses of the two liquid phase areas of the systems on the phase diagram were proportional to the ratio of the number of oxygen atoms to that of carbon atoms (O/C) in the molecules of the cyclic ethers, The distribution ratio of the ethers in methanol/heptane phases was related to the O/C ratio as well. Results were also successfully correlated using the NRTL equation.