Abstract: The circular target tunnel accesszone luminance measurement center of the tunnel affected by the natural environment caused by gray information of the current circular area of the tunnel accesszone luminance value is not accurate, a method of automatic identification of tunnel entrance based on image processing was proposed. The microprocessor can identify the tunnel hole and select the circular target areaautomatically, whichcan make the measured brightness value return to normal. The image was collected with camera in this method. And then image processing technologies were used to automatically identify the tunnel entrance by using a microprocessor (raspberry pie).Finally, the outside tunnel brightness value returned to normal according to the gray value of the circular target area when the circular target area of the tunnel hole was selected. The results show that this method can identify the tunnel hole accurately and which has been used in the high-speed pig Valley Tunnel of Guangxi successfully.