To date, most of fabricating processes of efficient perovskite solar cells (PSCs) have been carried out in high vacuum conditions or nitrogen protection atmosphere. Here we report a simple and novel strategy to fabricate efficient and stable ZnO-based PSCs. Firstly, ZnO nanoparticles were prepared by zinc acetate hydrolysis in methanol, and then the growth of methylamine lead iodide (CH₃NH₃PbI₃) crystal layer was realized by a two-step method. With aging treatment of ZnO film, high-quality ZnO/CH₃NH₃PbI₃ bilayer was obtained. Most importantly, the fabrication, measurement and store of solar cells in our processes were totally carried out under ambient conditions without a high vacuum or oxygen-free and water-free environment. A maximum efficiency of 9.4% was achieved. Moreover, the prepared devices exhibited promising stability at 30% humidity and 25 °C without any protection. We believe that the proposed strategy would push the applications of PSCs.