Method One:
1, enter the Win8.1 Control Panel, and then enter the "Power Options" setting, the following schematic.
2, and then in the Power option settings, change the current power plan settings, will be enabled by the use of brightness off, the following schematic.
The above settings, you can successfully turn off the Win8.1 screen brightness automatically adjust, and then you can keep the screen brightness is constant, if you want to adjust the brightness of the screen, you need to manually adjust it.
Method Two:
1, the use of Win + R combination of shortcut keys (Win8.1 under the Windows shortcut key combination shortcut key encyclopedia), the Call Run dialog box, and then open the following type of command: Services.msc, after the press ENTER, open Local service management, the following schematic.
2, in the Local Service settings, find the Sensor Monitoring service option, double-click on it, in the pop-up shot, choose to stop and disable the service can be, the following figure.