To quantitatively evaluate the influence factors of regional runoff, a field base was constructed, and field data about the rainfall, evapotranspiration, soil moisture, groundwater table, and surface water dynamics were collected in two different experimental sites of the Taihu Basin, China. Through the analysis of water balance in different rainfall runoff processes, it was found that the Dunne overland flow was the dominant mechanism responsible for the rapid runoff generation. The total rainfall and runoff expressed a good linear relationship with an R2 of 0.95 in the Hongqiwei test site. In addition, the initial groundwater depth was considered as the indicator of the antecedent soil moisture estimation for the close linear relationship that indicated the strong interaction between shallow groundwater and soil moisture. The depression storage was recommended in a range from 4.72 to 8.03 mm according to an estimation based on the water balance analysis for each rainfall event，which proves that the depression storage should not be neglected when calculating the runoff generation process in plain areas.