Pocket parks, as the main places for urban residents’ daily recreation and communication, are usually arranged near urban roads for the convenience of residents, ignoring the risk of residents being exposed to traffic air pollution. Therefore, studying the potential pollution exposure of pocket parks is of great significance for reducing residents’ exposure to air pollution and improving the health level of pocket park leisure activities. This paper carries out empirical research on the case of Qicai Pocket Park in Mianyang City from the perspective of PM2.5, a traffic-derived air pollutant. Based on PM2.5 monitoring and population activity statistics, a pollution exposure assessment is conducted on the public space nodes with dense population activities in Qicai Pocket Park, and the following conclusions are drawn: During the study, the average daily PM2.5 concentration in Qicai Pocket Park is higher, and some spatial nodes with highly intensive population activities have higher pollution exposure; Meanwhile, the spatial and temporal distribution of PM2.5 is significantly different, which is significantly correlated with urban roads, plant allocation and surrounding human activities. Based on the principle of population exposure assessment, this paper constructs a pollution exposure assessment method for pocket parks, in order to provide a scientific basis for improving the health quality of urban public space and optimizing the planning and design of pocket parks.