To simulate the influences of road surface runoff and drainage system overflow on road waterlogging, 2D surface runoff model is adopted for road catchment areas, 1D model is adopted for other catchment areas and underground pipe networks, and then a 1D and 2D coupling waterlogging model is developed based on PCSWMM. A quantitative source analysis method for road waterlogging is also proposed, which takes the contribution ratio of surface runoff from local road or overflow from drainage system to road waterlogging water as the indexes. After calibration and validation based on the measured water level in the manholes and the measured waterlogging depth on the road, the model is used to simulate the road waterlogging in a drainage area of Nanshan District of Shenzhen City under designed storm events. The results indicate that there are four main road waterlogging points (A, B, C, D) in the study area; overflow occurs on two points (A, D) under the storm event with a return period of 5 years, the overflow volume accounts for 24% and 61% of the total volume of waterlogging water respectively; while overflow occurs on three points (A, C, D) under the storm event with a return period of 50 years, the overflow volume accounts for 49%, 62%, and 73% of the total volume of waterlogging water, respectively; and the contribution of the overflow volume from manholes to the total waterlogging volume increases as the storm intensity increases. The dynamic change of road waterlogging is comprehensively affected by many factors such as the sources of waterlogging water, downstream blockage, local terrain and so on. For the waterlogging points where overflow volume accounts for a large amount of waterlogging water, it is recommended to improve the drainage capacity of the drainage system and promote the sponge city construction in the upstream catchment; for the waterlogging points where the local road surface runoff volume accounts for a relatively large amount of waterlogging water, it is recommended to promote the sponge city construction in the local area, and properly modify the local terrain or increase pump stations for drainage.