Dion-Jacobson (DJ) phase 2D perovskites with various aromatic diammonium cations, potentially possessing high stability, have been developed for optoelectronics. However, their stability does not meet initial expectations, and some of them even easily degrade into lower-dimensional structures. Underlying the stability mechanism and dimensional reduction of these DJ 2D perovskites remains elusive. Herein, we report that π-π stacking intensity between aromatic cations determines structural stability and dimensional variation of DJ 2D perovskites by investigating nine benzene diammoniums (BDAs)-derived low-dimensional perovskites. The BDAs without intermolecular π-π stacking form stable DJ 2D perovskites, while those showing strong π-π stacking tend to generate 1D and 0D architectures. Furthermore, the π-π stacking intensity highly relies on molecular symmetry and electrostatic potential of BDAs; namely, asymmetry and small dipole moment facilitate alleviating the π-π stacking, leading to the formation of DJ 2D perovskites and vice versa. Our findings establish the relationship of aromatic diammonium structure-π-π stacking interaction-perovskite dimensionality, which can guide the design of stable DJ 2D perovskites and the manipulation of perovskite dimensionality for various optoelectronic applications.