Airborne allergenic pollen can cause pollinosis and aggravate every year through repeated exposure in the pollen seasons, endangering human health and even life in severe cases. Allergenic pollen plants have been widely introduced and cultivated in cities, leading to a sharp increase in the number of urban pollinosis patients. In this study, based on the investigation data of 600 plots in the built-up area of Shenzhen as a case study, the species composition and the spatiotemporal distribution of allergenic pollen plants were analyzed, and the potential allergenic hazard with its distribution characteristics was evaluated by constructing calculation formulas of pollen concentration and pollen allergenic potential. The results showed that: ① In the built-up area of Shenzhen, a total of 186 species of allergenic pollen plants from 46 families and 92 genera were recorded. Among the allergenic pollen plant species, 43.37% were alien species, with 81.00% of them originated from America, Asia, and Oceania. The number of allergenic pollen plant species was highest in park green space, up to 126. Allergenic levels were mainly graded Ⅰ, covering 154 species. ② The peak bloom stages of allergenic pollen plants were spring and summer, with flowering species accounted for 65.02% of the annual total. The peak month appeared in August, concerning 92 flowering species. ③ August had the highest potential value of pollen concentrations, accounting for 12.13% of the annual year total. The contribution of Leguminosae and Poaceae were relatively high, respectively, accounting for 40.86% and 64.13% of the arbors and the herbs totals. The values in the Longgang District were relatively high in all seasons, reaching 26.06%-29.42% of respectively seasonal total. ④ The allergenic hazard levels in all plots were not high in winter and spring, but some plots reached second-level severe in summer and autumn. The hazard levels of investigated plots in the Luohu District were relatively low throughout the year. In contrast, those of investigated plots in the Guangming District were relatively high in spring, summer, and autumn. The high-hazard-level plots mainly appeared in the subsidiary green space and park green space. ⑤ Results of scenario-simulation for allergenic pollen plants prevention and control measures showed that the effect of removing major allergenic pollen plant species might be better than that of reducing the pollen concentrations of all allergenic pollen plant species. This study provides a reference for the management, planning, and maintenance of urban allergenic pollen plants, and the research and solution of urban pollen allergenic problems.