Abstract: Interaction between surface water and groundwater has always been a hot topic in hydrogeological researches. Previous studies focused on the hyporheic zone of rivers, but the hypolentic zone of lakes with relatively static water bodies was seldom examined. The Baiyangdian Wetlands is taken as a pilot area in this study, and a monitoring system of water table and temperature is set up. The vertical interaction fluxes between surface water and groundwater is quantified by using a heat tracing method. According to the Darcy’s Law, the vertical coefficient of permeability is calculated inversely. Based on the heat tracing method and the Darcy’s Law, a way of quantifying vertical interaction between surface water and groundwater is summarized. The results show that infiltration from surface water to groundwater around the banks of the Baiyangdian Wetlands is dominant in the interaction procedure. The total infiltration velocity from surface water to groundwater during the monitoring period ranges from 0.2 to 1.1 cm/d, and the vertical hydraulic conductivity, from 0.038 to 0.912 m/d. The conclusions in this paper can provide data support for strategy of water diversion and protection of eco-environment in the Baiyangdian Wetlands.