A method for processing a traffic monitoring video image in a foggy day includes: 1, detecting vehicles in traffic monitoring scene; 2, building area-of-interest, namely a driving area according to detected vehicle and pedestrian movement areas; 3, estimating road area depth ratio, and generating a depth image: estimating the road area depth ratio according to detected sizes, positions and moving directions of vehicles, building a traffic monitoring scene model, and generating a traffic monitoring scene depth image automatically; 4, building a traffic monitoring scene foggy day image degradation model: using the traffic monitoring scene depth image as an important parameter of foggy day image degradation, and building the traffic monitoring scene foggy day image degradation model; and 5, solving the traffic monitoring scene foggy day image degradation model, and recovering an image.