Runoff formation processes at the experimental plot (1600 m²), the field (0.06 km²), and the small catchment (1.36 km²) with shallow groundwater table and dense drainage system in North Huaihe River Plain (the northern part of the Huaihe River Basin, China) were analyzed based on observed rainfall, runoff and groundwater table depth data of 30 storm events during the flood seasons from 1997 to 2008. At the outlet of the furrow of the experimental plot, only the surface runoff was collected and measured, whereas both the surface and subsurface runoffs were collected at the drainage ditches outlets of the field and the small catchment. The present study showed that the relatively narrow range of rainfall amounts resulted in significantly different runoff amounts at all the three scales. When the ground water is close to surface, the runoff amount is a great percentage of rainfall amount. Significant linear relationships between the difference of rainfall and runoff amounts and the changes in water table or the initial water table depth were found. When the 30 events were divided into three groups with initial water table (as a parameter indicating the antecedent moisture condition) shallower than 0.5 m, deeper than 2.3 m or between 0.5 m and 2.3 m, significant rainfall-runoff relationships existed for each group. These imply that saturation-excess surface flow dominated the runoff response, especially when water table is shallow. For almost all the events, the water table rose above the bottom of drainage ditch during the event, and the total runoff amounts were larger at the field and the catchment than that at the plot with only surface flow measured, showing a great contribution of subsurface flow. Groundwater table depth, not only reflecting the antecedent moisture conditions, but also influencing the lateral sub-surface flow to the drainage ditches, would be an important parameter dominating runoff formation process in catchment like the study area with shallow water table and dense drainage system