Current map-matching algorithms consider more about the common plain road networks. The overpass always be ignored or treated as normal intersection without considering its complex topological structure. In order to fill this gap in map-matching area, the POMM (Precise Overpass Map-matching Model and Algorithm) is proposed in this paper. A novel overpass model is built for the overpasses map-matching algorithm. This model divided the overpass into straight roads and curve ones which consist of a set of directional points. According to the match degree for each straight road or directional point, the optimum road can be selectd from the candidate roads. Finally, the vehicle can be matched to the actual position on the optimum road. Experiment results of Jinan Bayi overpass using the actual GPS data shows that the algorithm has efficiency in accuracy (over 95%) and can precisely find the actual position of the vehicle in the overpass road, especially for the curve roads.