Atomically thin MoS2 films have attracted significant attention due to excellent electrical and optical properties. The development of device applications demands the production of large-area thin film which is still an obstacle. In this work we developed a facile method to directly grow large-area MoS2 thin film on SiO2 substrate via ambient pressure chemical vapor deposition method. The characterizations by spectroscopy and electron microscopy reveal that the as-grown MoS2 film is mainly bilayer and trilayer with high quality. Back-gate field-effect transistor based on such MoS2 thin film shows carrier mobility up to 3.4 cm2 V−1 s−1 and on/off ratio of 105. The large-area atomically thin MoS2 prepared in this work has the potential for wide optoelectronic and photonic device applications.