The improvement of power conversion efficiency (PCE) and stability of perovskite solar cells (PSC) relies on the enhanced quality of perovskite layer and the modification of its adjacent interfaces. For this purpose, a multifunctional organic passivation molecule 1-(4-Fluorophenyl) biguanide hydrochloride (F-BHCl) is introduced to the top and bottom interfaces of the perovskite layer. The PCE of PSC after the modification of double interfaces with F-BHCl is significantly increased from 22.41% (unmodified) to 25.14%, and the storage, thermal, and operation stability is also improved. The comprehensive theoretical and experimental studies verify that due to its versatile functional groups and adaptation, F-BHCl can significantly improve the quality of perovskite film, fully passivate several kinds of common defects, smoothen the top surfaces of perovskite film, and construct “molecular bridges” with carrier transporters on both the top and bottom surfaces, leading to significantly reduced non-recombination and carrier transport losses. As a result, a significant increase is achieved in the open circuit voltage and fill factor as well as the whole performance of the device.