The invention discloses an expressway driving early warning system and method. According to the invention, respective satellite positioning data of a key vehicle early warning device and a common vehicle early warning device is sent to a background data processing system; and the background data processing system determines whether the distances between key vehicles, and between key vehicles and common vehicles and the relative speed meet an early warning condition and sends corresponding early warning information to the key vehicle early warning device and the common vehicle early warning device, thereby achieving objectives that possibly occurring dangers can be warned earlier and avoided in advance and driving safety on the expressway is improved. According to the invention, by use of information technology of mobile Internet, real-time continuous tracking and monitoring of vehicle running states are achieved; the function that beyond visual range running early warning function based on early warning scene real-time identification is achieved; and occurrence of accidents of collisions and rear-end collisions on the expressway can be effectively reduced.