The invention discloses a self-sensing dimming tunnel lighting system and a dimming control method of the system. The self-sensing dimming tunnel lighting system includes a luminance detection module, a data processing module, a dimming module and an illumination module. The luminance detection module is used to detect luminance information at several positions of a tunnel, the data processing module outputs a dimming control signal to the dimming module according to the luminance information and a prestored relative luminance list, the dimming module outputs a power control signal to the luminance module according to the dimming control signal, and the luminance module controls output power of a plurality of light sources in the tunnel according to the power control signal. The detected luminance information of the tunnel and prestored relative luminance list are integrated to realize intelligent control of output power of light sources in the tunnel, so as to adjust the luminance of each position in the tunnel. When users drive in and out of the tunnel and pass through the tunnel, no matter it is sunshine in the day or quiet in the night, a bright, clear and smooth visual effect of lighting is provided in the tunnel.