Perovskite solar cells have become a research hotspot in the field of new energy due to the excellent performance and potential in application, but it still displays some disadvantages such as high defect density and poor stability.In this study, L-arginine, a small molecule of organic matter, was doped into the perovskite precursor solution as compared with the other amino acids, and the perovskite solar cells were prepared by a two-element and two-step preparation method.The test results show that L-arginine doping improves the photoelectric performance of the device, which photoelectric efficiency increases from 18.81% to 21.86%.L-arginine reduces the nonradiative recombination of carriers and increases the average carrier life by reducing the defect density of perovskite layer from 4.83×10 16 cm -3 to 3.45×10 16 cm -3 .In addition, the perovskite grain size increases, grain boundaries decrease, the light absorption ability and stability of the film are enhanced, while the hysteresis effect is suppressed.Improvement of the photovoltaic performance is due to the passivation of defects by interaction between multi-groups of L-arginine and perovskite materials.This study provides an optimization method for perovskite solar cells.