Being an important part of planar heterojunction perovskite solar cells (PSCs), electron transport layer (ETL) plays important roles in enhancing the photovoltaic performance and stability of PSCs. Despite the two most commonly used ETL materials, titanium dioxide (TiO₂) and tin oxide (SnO₂) all being nanoparticles and fabricated through solution method, TiO₂ suffers from low electron mobility, large device hysteresis, weak chemical stability and high-temperature processing. By comparison, SnO₂ owns the advantages of excellent optoelectronic properties, greater stability because of its chemical inertness and low-temperature processability. We focus on the stability and interfacial charge extraction in PSCs based on SnO₂ ETL. First, physical properties and advantages of SnO₂ are reviewed. Then, starting from the preparation and film formation methods of SnO₂ (e.g. chemical bath deposition, solution spin-coating, etc.), we further discuss the bulk and surface defects of SnO₂. Finally, targeting the defect profiles of SnO₂ ETL, we emphasize regulatory approaches to enhance the device stability and carrier extraction in PSCs based on interfacial passivation, bulk doping and double-ETL structures. This review article contributes to the further advancements of device performance and stability of PSCs, and provides insights for the practical application of this emerging photovoltaic technology.