The optical properties of liquid crystal molecule system have been investigated by molecular dynamics (MD) simulation and density functional theory (DFT) through the Maier-Meier theory.5CB (4-Cyano-4-pentylbiphenyl) was used as a benchmark molecule to demonstrate our calculation results because the complete data bases of optical properties can be obtained in previous experimental papers.The order parameter, average density, and averaged volume of a 5CB molecule were predicted by molecular dynamics simulation with the COMPASS potential.