To enhance the operational efficiency and system collaboration capability of transportation networks in smart cities, a multi-source data fusion and optimization method based on big data technology is studied, and a four level linkage model including signal timing, route adjustment, resource reconfiguration, and diversion regulation is constructed. Taking the central urban area of Jiangnan as an example, the strategic effects under multiple scenarios were analyzed, and the results showed that the multidimensional optimization system significantly improved traffic delays, road network traffic, and bus on-time performance.