The molecular structure and stacking mode relationship is the core of creating planar layer-stacked materials by crystal engineering. However, it remains highly challenging to clarify the relationship. By exhaustively extracting 50 compounds with D2hor D3hmolecular point groups from the Cambridge Structural Database, we study in this work, the characteristics of planar layer-stacked molecules and those of others for comparison. For a hydrogenous molecule, it requires both a strong donor and acceptor of hydrogen bonds (HBs) therein and both large positive and negative electrostatic potential extremes (e.g., ≥35 kcal/mol at the theoretical level of B3LYP/6-311G(d)) situated on its edge for planar layer stacking, while regarding the H free molecules stacked in planar layers, they are prone to be sparsely arranged, and the intralayer intermolecular interactions belong to weak halogen bonding or other weak van der Waals attraction, with rather small electrostatic potential extremes on their edges and/or faces. Additionally, we first propose the definitions of six types of stacking modes to scientifically and exactly classify them based on the relative orientations and arrangement of molecular planes in the crystal. Accordingly, a strategy for constructing planar layer stacking with strong HBs is proposed. This work is expected to benefit the crystal engineering of planar layer-stacked materials.