Taking the downtown area of Longyan in Fujian as an example, based on the LID module in SWMM model, this paper simulated 10% of Rain Garden, 20% of Green Roof,15%of Permeable Pavement and a combination measure (including 3% Rainwater garden, 7% green roof and 5% infiltration pavement) to analyze the reduction rate, including the reduction of efficiency and sensitivity to precipitation over time,of the total runoff, peak flow and pollutant load in the upper, middle and lower reaches (denoted as A, B and C) of the central urban area of Longyan City, Fujian Province. The comprehensive evaluation was carried out by introducing the weighting coefficient. Based on the spatial difference of the drainage area, the LID optimal layout scheme of each drainage area is finally determined. The results show that the A area should select the green roof scheme, the B area should select the best combination scheme, and the C area should choose the rainwater garden scheme.