The invention discloses an expressway vehicle overspeed snapshot system based on Internet of Things and belongs to the technical field of intelligent transportation vehicle snapshot.The system comprises a traffic monitoring terminal, a coordinator, routers and ZigBee wireless network nodes, all the ZigBee wireless network nodes are arranged on an expressway at equal intervals, each ZigBee wireless network node comprises a ZigBee module, a vehicle speed detection unit, a control unit and an image acquisition unit; each image acquisition unit comprises an image snapshot module, an image transmission module and an image storage module; each image transmission module comprises a first double-convex lens with the focal distance being f1 and a second single-convex lens with the focal distance being f2, wherein one or more surfaces of each first double-convex lens and the corresponding second single-convex lens are provided with binary diffraction optical structures, and the ratio of f1 to f2 is 0.25-1.36.By means of the expressway vehicle overspeed snapshot system, automatic real-time monitoring can be conducted on the expressway for 24 hours, and a shot picture is high in resolution ratio.