The emergence of hybrid organic–inorganic metal halide perovskite solar cells (PSCs) causes a breakthrough in the solar technology recently due to its superior optoelectronic properties and the low-cost fabrication processes. The dramatic enhancement in power conversion efficiency (PCE) of PSCs from 3.8% in 2009 to the recent certified record PCE of 22.7% indicates huge potential of PSCs for future high efficiency and large scale photovoltaic manufacturing. The electron selective layer (ESL) plays an important role in electron extraction and hole blocking function in PSCs, and there have been great interest in developing efficient ESL materials. Recently, tin oxide (SnO2) as an ESL has attracted significant research attentions owing to its low temperature preparation processes as well as yielding high PCE and good stability of PSCs. In this perspective article, we focus on the development progress of SnO2 as an ESL in PSCs, and discuss the strategies for preparing SnO2 to achieve PSCs with high efficiency, less hysteresis and good device stability.