The invention provides a server humidity control device which comprises a desiccant placing box and a server. A desiccant water swells and exerts lateral pressure on a moving plate of the desiccant placing box. The moving plate moves away from a fixed plate until a first conductive protrusion contacts a second conductive protrusion. The server receives a low level signal transmitted by a data transmission interface, and sends an alarm message to a preset mobile phone terminal to prompt a mobile phone terminal user to replace the desiccant. Due to the structure of the desiccant placing box, thedevice provided by the invention accurately knows the effective cycle of the desiccant and ensures that the server operates in a dry environment.