The invention discloses a sedan car co-running system and method, and relates to the technical field of mobile communication and the Internet. The car sharing system comprises a user client, a driverclient, a server and a carrier loader. The server comprises an information storage module, an information processing module, an information transceiving module and an expense settlement module; the carrying vehicle is provided with a passenger carrying area and a vehicle carrying area. The car sharing method comprises the following steps that 1, a user fills in demand information; 2, the server matches an order for the user; 3, the user pays before the payment cut-off time point; and 4, informing a user and a driver that the order is established. According to the invention, cross-city car sharing travel is realized through a unified transportation mode of the carrier loader; a plurality of cars and corresponding passengers can be carried on the carrier loader, so that the traffic flow pressure on the expressway is relieved, the road toll cost of the cars on the expressway section is reduced, the driving fatigue of car drivers on the expressway section is avoided, and free use in the whole process is realized.