The invention discloses a comprehensive early warning system for urban overpass ramps. The comprehensive early warning system comprises a control system, a display device, an information collection device, and a deicing spray system. The control device comprises a computer control system and a PLC control system. The computer control system is connected with the PLC control system. The information collection device comprises multiple groups of pavement state sensors and picture taking cameras. The deicing spray system comprises nozzles arranged on both sides of the pavement of an overpass at intervals, deicing liquid storage tanks, and a spray pipeline connecting the nozzles and the deicing liquid storage tanks. The display device comprises an LED display device arranged at the entrance of a ramp and LED warning lamps arranged in parallel along the ramp. The picture taking cameras take pictures of and sample the pavement of the overpass, and send the pictures taken to the computer control system. The computer control system identifies the pictures and judges the road condition, and then controls the operation of other components according to the result of judgment.