Flexible perovskite solar cells based on polyimide as the substrate can be used in aerospace vehicles due to their excellent thermal stability and high power-to-weight ratio. However, the metal electrodes of polyimide cause an increase in non-radiative recombination in perovskite solar cells, thereby degrading the performance of perovskite solar cells. In this paper, we propose a method of fabricating flexible perovskite solar cells with polyimide as the substrate based on the ITO modification strategy. By depositing a layer of ITO on the metal electrode, not only is the ratio of Ni³⁺/Ni²⁺ in the hole transport layer improved, enhancing the conductivity of the hole transport layer, but also the film-forming quality of the perovskite layer is improved, and the non-radiative recombination at the interface between the perovskite film and the hole transport layer (HTL) is suppressed. The flexible perovskite solar cells based on ITO modification strategy have a conversion efficiency of 17.91%. This work provides an effective strategy for fabricating high-efficiency flexible perovskite solar cells.