A method for determining the position of a mobile node, applied to a roadside unit, RSU,, wherein the RSU and a plurality of mobile nodes form a communication network on a road, the method comprises: obtaining, by at least one sensor of the RSU, first road information, wherein the first road information provides absolute position distribution information as a GPS position representing a road topology associated with the mobile nodes; receiving, by a communication device of the RSU, second road information from a first mobile node of the mobile nodes, wherein the second road information provides relative position distribution information associated with the first mobile node and second mobile nodes adjacent to the first mobile node; and determining, by a comparison device of the RSU, a position of the first mobile node on the road according to the first road information and the second road information and marking an ID of the mobile node on a corresponding position to identify the mobile node and record the position of the mobile node, wherein the second road information further provides position information corresponding to the first mobile node and the step of determining the position of the first mobile node on the road according to the first road information and the second road information using the comparison device comprises: determining a further mobile node for whose position no mobile node ID is present and, subsequently, retrieve a to be mapped star topology, G, centered on said further mobile node, x, which has not been compared by using the GPS position of said mobile node and a possible error distance of the GPS position; selecting a third mobile node, u, closest to the mobile node x, obtaining a portion of the first road information according corresponding to a star topology as third road information, wherein the third road information is centered on a third mobile node; and checking whether a correlation distance and an angle of the neighboring nodes in the third road information centered on the third mobile node is the same as the one in the second road information centered on the first mobile node, and if yes, determining that the position of the third mobile node is the same as the position of the first mobile node. obtaining, by at least one sensor of the RSU, first road information, wherein the first road information provides absolute position distribution information as a GPS position representing a road topology associated with the mobile nodes; receiving, by a communication device of the RSU, second road information from a first mobile node of the mobile nodes, wherein the second road information provides relative position distribution information associated with the first mobile node and second mobile nodes adjacent to the first mobile node; and determining, by a comparison device of the RSU, a position of the first mobile node on the road according to the first road information and the second road information and marking an ID of the mobile node on a corresponding position to identify the mobile node and record the position of the mobile node, wherein the second road information further provides position information corresponding to the first mobile node and the step of determining the position of the first mobile node on the road according to the first road information and the second road information using the comparison device comprises: determining a further mobile node for whose position no mobile node ID is present and, subsequently, retrieve a to be mapped star topology, G, centered on said further mobile node, x, which has not been compared by using the GPS position of said mobile node and a possible error distance of the GPS position; selecting a third mobile node, u, closest to the mobile node x, obtaining a portion of the first road information according corresponding to a star topology as third road information, wherein the third road information is centered on a third mobile node; and checking whether a correlation distance and an angle of the neighboring nodes in the third road information centered on the third mobile node is the same as the one in the second road information centered on the first mobile node, and if yes, determining that the position of the third mobile node is the same as the position of the first mobile node.