The invention discloses a road congestion recognition visualization method based on DBSCAN+. According to the method, first, a large amount of uploaded data of OBD vehicle terminals of floating cars in a city is preprocessed and cleaned; slow travel GPS track point data in a unit time period is extracted according to instantaneous velocities of the floating cars; DBSCAN+ algorithm parameters are set, and initial class cluster blocks in a slow travel region are acquired through parallel clustering of extracted data points; by calculating surface distances among all the data points in each classcluster block respectively, the two farthest points in each class cluster block are found out, and line segments are fitted; map-matching deviation rectification is performed on the fitted line segments according to a topological relation among all road segments in an actual road network; and last, by calculating travel distances of different vehicles in the unit time period in each class clusterblock respectively and calculating average travel distances synthetically, the congestion degrees of all the class cluster blocks are judged and expressed in different colors for differentiation andvisualization. The method can adapt to large-scale city taxi OBD terminal GPS track data, brings convenience to real-time recognition of city road congestion through taxi running conditions and achieves a good visualization effect.