The present invention discloses a liquid crystal display panel, liquid crystal display device, photo detecting device and light intensity adjustment method. The liquid crystal display panel comprises a plurality of first scan lines, a plurality of first data lines, a plurality of first thin film transistors, a plurality of liquid crystal pixel units and a built-in photo detecting module. The plurality of first thin film transistors are respectively disposed at intercrosses of the plurality of first scan lines and the plurality of first data lines, and each of the first thin film transistors is connected to the first data line and the first scan line. Each of the first thin film transistors is used to drive a liquid crystal pixel unit. The built-in photo detecting module detects light and outputs a multi-bit digital signal corresponding to the intensity of the light.