Molecular crystals materials are unique and versatile with diverse application in pigments, organic electronic and pharmaceuticals and explosives. Since the constituent molecules are bound by weak van der Waals interactions, the same molecule could crystallize in variety of polymorphs. The stable structure among them could be predicted by using the genetic algorithm (GA). For instance, Noa Marom et al. develop a package using GA to generate off-spring structure from the properties of selected parent structure(s), the structure optimization and total energy calculation are performed by density functional theory. We have tried to repeat their result using their code but with modification (instead of density function theory, we use molecular dynamic). Using a genetic algorithm combined with other structure optimization method, molecular crystal structures with high stability could be generated for further application.