The statistical counting method for the computer simulation of the ther-modynamic quantities of polymer solution has been reviewed. The calculating results fora single athermal chain confirm the theory of the renormalization group. The results forthe athermal solution are consistent with the scaling law of the osmotic pressure with theexponent 2.25. The results for a single chain with the segmental interaction are in a goodagreement with the exact results obtained by the direct counting method. The results for a single chain with the segmental interaction are in a good agreement with the exact results obtained by the direct counting method.The results for the polymer solution show us that the Flory-Huggins parameter is strongly dependent on both the polymer concentration and the interaction energy between segments.