Molecular simulations were performed to investigate the molecular structural effects on needle coke mesophase stacking. The simulation results showed that the stacking states of anthracene trimer and tetramer accumulations were orderly, while the stacking states of anthracene dimer, pentamer, and hexamer accumulations were disorderly. Anthracene trimer and tetramer in the model compounds were two of the most ideal needle coke mesophase constituents. It was also found that the introduction of methyl side chains in anthracene trimer derivatives was not conducive to the formation of a mesophase crystal. To sum up, the molecules which had similar structures to anthracene trimer or tetramer with no alkyl chains are ideal constituents of needle coke mesophase.