The electron transport layer is very important for the device efficiency and stability of perovskite solar cells. Tin dioxide is a common electron transport layer in high-efficiency solar cells and has good carrier extraction and transport capability. However, using the solution method to prepare tin dioxide, a large number of defects are generated on its surface during high-temperature annealing in air, which can degrade the electrical properties of the film, so the solution method is not conducive to preparing large-area film. In this paper, the reactive plasma deposition method is used to prepare tin dioxide thin film, and the performance of the thin film is optimized by adjusting the glow discharge time and working current. The film is applied to small-area N-I-P type perovskite solar cells, the efficiency reaching to 21.24%. The hysteresis of the device is improved by introducing stannous isooctanoate and tin dioxide as a double electron transport layer, the open circuit voltage of the solar cell increases from 1.11 to 1.15 V, the efficiency rises from 21.27% to 22.15%, and the hysteresis factor decreases from 24.04% to 3.69%. This work presents a new preparation method and effective optimization strategy to prepare tin dioxide electron transport layer, which will promote the development of planar heterojunction perovskite solar cells and provide a new research idea for preparing high-efficiency and stable perovskite solar cells.