The combinatory entropy in the ternary solution of crystalline polymers (2), with n(c) rod-like parts and c segments per part, with solvent (1) and holes (0) has been derived based on the Flory-Huggins theory, which is given by : [GRAPHICS] where R is the gas constant, z is the coordination number, e is communal entropy, m=r-n(c)(c - 1), A = [phi0 + phi1 + (phi2/r)], theta = n(c)c/r, r is the total number of segments per polymer chain, and phi(i) is the volume fraction of component i. Two types of cluster formation by the rod-like parts in the crystalline polymer solution are considered : cluster formations by different polymer chains, and by a single polymer chain. Dependence of the cluster size on the length of the rod-like part or c has been determined based on the theory. An equation for the entropy of fusion for arbitrary crystallinity is also derived.