Urbanization is leading to significantly increased pollution of suspended particulate matter (PM) in urban street canyons, affecting residents’ health and the urban environment. In this paper, the distribution characteristics of PM in urban street canyons are discussed, and optimized design strategies are proposed, with the Shapingba Railway Comprehensive Transportation Hub Area in Chongqing as the research object. The study selected summer and winter as typical periods. It obtained the concentration data of suspended particulate matter under different street canyon morphologies, traffic flow, and meteorological conditions using high-precision monitoring equipment to collect PM2.5 concentration. It was found that the PM2.5 concentration in summer and winter in the Shapingba Railway Comprehensive Transportation Hub Area showed obvious daily change rules and was significantly affected by the spatial morphology of the street canyon. Based on the actual monitoring results, this paper proposes a strategy to optimize the spatial morphology of urban street canyons, aiming to reduce the accumulation of suspended particulate matter and improve the quality of the urban environment. The research in this paper not only provides a theoretical basis for the control of suspended particulate matter in urban street canyons but also provides practical guidance for environmental protection in urban planning and architectural design, which is of great significance for improving the quality of the living environment for urban residents.