Molecular interactions are the key to understanding the structure and properties of materials. Also, it is critical of chiral recognition. Since the molecular interactions at play in chiral discrimination is difficult to investigate under traditional experiment conditions. We have undertaken a computer experiment of van der Waals interaction between chiral molecules and a polymer, which works for chiral separation. Building molecular models, choosing proper force field and Monte Carlo method, we have calculated the difference of interaction energy between isotactic poly (triphenylmethyl methacrylate) and (+) hexahelicene or (-) hexahelicene. It is finally found about 1.379 4 kJ/mol between the polymer and the two chiral hexahelicenes. Reasonably, this difference is regardd as the main reason which induced chiral separation. Furthermore, we compared the results from computer smulation with that from experiment. It can be seen that some details during chiral separation process, such as trailing effect, can also be predicted, and be consistent with the experiment results. Finally, the effective structureal characteristics of the recognition site are pointed out.