Abstract: A general relationship among the Gibbs free energies of intermediate compounds has been theoretically derived for n (≥2) -component systems. Accordingly it has been reached that the Gibbs free energies of intermediate compounds vary with the molar fractions of components in a certain regulation. In a binary system, the regulation is a quosi-parabola. In a ternary system, it is a quosi-paraboloid, and in n (≥4) -component systems, generally their regulations can not be geometrically descriced.