A control method and a device thereof are provided, which are applied to an electronic device. The electronic device includes a display module and a projection module, and is capable of displaying output content through the display module or projecting the output content to a projection screen. The method includes: detecting a state of the projection module; acquiring a current display brightness of the display module as a first display brightness, in the case that it is detected that the projection module is controlled to perform projection; and controlling a display brightness of the display module to switch from the first display brightness to a second display brightness which is lower than the first display brightness.