Perovskite solar cells(PSCs) have achieved more than 25% efficiency in just a decade, which are of great commercial value. This is because the three-dimensional(3D) perovskite(PVK) layer has many advantages, such as suitable bandgap, high absorption coefficient and long electron diffusion length. However, unstability is still an urgent problem to be solved in 3D PSCs. Comparing with 3D perovskite materials, 2D perovskite crystals have recently attracted increasing attention due to some unique properties for improving stability. The hydrophobic bulky alkylammonium cations in 2D perovskite lattices can block the accessible pathways of moisture invasion, making them promising candidates for optoelectronic devices. Meanwhile, due to the tolerance of 2D perovskite to organic and inorganic elements, its chemical composition and energy band also change. This review highlights the importance of energy bands in 2D PSCs and summarizes bandgap regulation and energy level alignment(ELA) of 2D perovskite, which plays an important role in guiding the preparation of high-efficiency and stable low-dimensional perovskite solar cells.