A single focus lens module includes a mechanical shutter taking lens assembly and there are front lens shutter module, taking lens and holder from the object side to the image side. The taking lens is connected to the holder by threading. The front taking lens assembly is connected the taking lens. The focus of the taking lens can be adjusted to a proper position by threads and the shutter module is then assembled. By this arrangement, the structure of the single focus lens module can be simplified and the precision of the assembly is improved.