With their excellent photoelectric properties, perovskite solar cells have become the most promising photovoltaic devices in recent years. However, owing to defects and energy level misalignment, the non-radiative recombination loss of the perovskite solar cell will increase, which hinders the its efficiency and operational stability from being improved further. Therefore, it is very important to reduce the loss caused by energy level misalignment for realizing high-efficiency perovskite solar cells. In order to solve the above-mentioned problems, perovskite solar cell with dual electron transport layer (ETL) is studied in this work. The dual-layer structure forms a stepped conduction band structure to reduce the conduction band offset between the active layer and the transport layer, which reduces the interface recombination between the two structures and improves device performance. In addition, the influences of the defect density on the cell performance for the two ETL structures are also discussed. With the continuous increase of the defect density, the performance of the single-layer structure decreases more obviously. While the dual ETL structure can alleviate the performance dependence on the defect density in comparison with the single ETL structure. Therefore, the use of dual ETL can improve the performance of perovskite solar cells and defect tolerance, which provides guidance for designing high-performance solar cells.