A method and a device are provided for adjusting signal strength of a router. In the method: the device monitors a number of terminals wirelessly connected to the router during a preset time period. The device determines a signal-strength level of the router according to the number of the terminals wirelessly connected to the router during the preset time period. The device adjusts the signal strength transmitted by the router according to the signal-strength level. Through the present disclosure, a router may automatically control the signal strength transmitted by itself.