Abstract: Under the background of systematic and full-field promotion of sponge city construction, the allocation of Low Impact Development（LID） facilities holds significant implications for urban stormwater management. In this study, we established a stormwater model for the Yixing City area in Jiangsu Province, utilizing the Storm Water Management Model（SWMM）. A comprehensive objective function was formulated, taking into account the reduction rates of runoff volume, Suspended Solids（SS） load, Life Cycle Cost（LCC）, and the area occupied by LID facilities. Through the assignment of weights to objective parameters in different scenarios, the multi-objective optimization problem was transformed into a single objective optimization problem, where each weight represented the priority of the corresponding objective parameter. The Genetic Algorithm（GA） was then applied to derive the optimal LID layout under diverse scenarios, to analyze and compare the impact of different priorities and recurrence periods of target parameters on optimization results. The results indicate that:（1） Under the same weight conditions, LCC exhibits a more pronounced impact on GA optimization calculations compared to LID area.（2）The spatial allocative optimization of LID facilities in small subcatchments located upstream is particularly susceptible to the rainfall return period. The research findings offer valuable insights for the spatial allocative optimization of LID facility and urban flood control in sponge city construction.