The invention relates to a transparent vehicle-mounted digital instrument controller and a display brightness controlling method of the transparent vehicle-mounted digital instrument controller. According to the transparent vehicle-mounted digital instrument controller and the display brightness controlling method of the transparent vehicle-mounted digital instrument controller, a transparent display screen is used, external light signals are collected through a light detection sensor, light and display brightness corresponding levels are set in the controller, in the use process, by adjusting the display brightness under the current light intensity, the controller can automatically set matching data of the display brightness under different degrees of environment brightness, and a display effect most suitable for a user is achieved. The brightness of a transparent vehicle-mounted digital instrument varies with the external light, so that the visual effect for people is better. By means of the transparent vehicle-mounted digital instrument controller and the display brightness controlling method of the transparent vehicle-mounted digital instrument controller, the visual effect of the transparent liquid crystal instrument under the variation of the environmental light can be optimized, and the visual requirements of different people can be met. The transparent instrument can automatically adjust the display brightness according to the variation of the intensity of the external light, the installation position of the transparent instrument is flexible, and driving sight is not affected even when the transparent instrument is installed in front of a windshield.