Co content plays a crucial role in the magnetic and electric properties in Co doped ZnO (ZnO:Co) films. In this work, the method of RF source-assisted molecular-beam vapour deposition was used to prepare ZnO:Co films with various Co contents. The doped Co2+, the metal Co, and the oxygen vacancies (Vo) were found in the deposited films. The surface roughness and the crystalline size of the ZnO:Co films also increased by using bigger Co content. The prepared ZnO:Co films show n-type conductivity and room temperature ferromagnetism. By increasing the Co content, the content of the metal Co exceeded that of the doped Co2+ gradually, which led to the higher electric conductivity, carrier concentration, mobility, and saturation magnetization.