In urban areas, the buildings and pavements make it hard for rainwater to infiltrate into the ground. The hardened underlaying sub-crust has increased the total rainfall runoff, pushing up the peak flood flow. Drawing on the construction concept of sponge city, this paper probes deep into the materials in each layer of permeable pavement for sidewalks. Specifically, a runoff model was constructed for sidewalk pavements under rainfall conditions through numerical simulation and model testing. Using the precipitation pattern of Qingdao, China, several combinations of materials were subject to rainfall simulations, revealing how each permeable pavement controls and affects the surface runoff. The results show that the permeability of surface course and sub-crust directly bear on the starting time, peak flow, total runoff and runoff time of sub-catchment runoff; and the latter has a greater impact than the former on sub-catchment runoff.