As a type of novel thin film solar cells, perovskite solar cells develope sharply within a decade, which efficiency has approached to that of the commercial silicon solar cells. However, its poor stability in the air has limited the further practical application. Herein, we achieve uniform sable perovskite films under open environment by adding some poly 4-vinylpyridine (PVP). The morphology, structure and performance test results show that the perovskite films added with PVP were more compact and uniform than the bare one. Moreover, the assembled solar cell with 0.4wt% PVP exhibited highly reproducible efficiencies up to 13.07%, much higher than that of 6.09% for the controlled one. When restored in the air with approximately 50% relative humidity in the absence of encapsulation, its efficiency decay time to a half from 3 d for bare one extended to 3 w. However, high PVP additives result in incomplete reaction between PbI₂ and CH₃NH₃I. If the above mentioned process is further optimized, is expected to be applied to the large-scale preparation of more stable perovskite film.