The combinatory entropy S-comb in complex polymer solution has been calculated based on a lattice model, An inter-molecular part of S-comb in solution of polymer consisting of rod and flexible parts S-inter,S-r-f is given by S-inter,S-r-f/R = SinterF-H/R + (1 - mc phi(2)/r) ln(1 - mc phi(2)/r) - phi(2)(1 - mc/r) ln(1 - mc/r) where S-inter,S-F-H/R = -(1 - phi(2)) ln(1 - phi(2)) - (phi(2)/r) In phi(2) is that in the Flory-Huggins theory, phi(2) is the volume fraction of the polymer and m the number of repeated units in a polymer chain. The repeated unit consists of a rod part and a flexible part and c and n are the number of segments in the rod part and flexible part, respectively, and the total number of segments per polymer chain is r. The S-inter,S-r-f in this work is essentially the same as that in the solution of rod-like particles derived by Flory except for the last term in S-inter,S-r-f. The combinatory entropy in the solution of star polymer S-inter,S-star calculated in this work is given by S-inter,S-star/R = S-inter,S-F-H/R - phi(2){(n - 1)/r} ln phi(2) where n is the number of branches per star polymer. The critical concentration phi(2,c) in solution of the star polymer calculated in this work is given by phi(2,c) = l/[1 + (r/n)(1/2)] which is larger than that in solution of linear polymer of the same molecular weight of the polymer, An effect of chain stiffness on the critical concentration is also discussed.