Abstract: The system of pumping & recharging well filled with gravel (PRWFG) is a specific type of the single thermal well used as ground heat exchanger. The heat efficiency of PRWFG is higher than that of the standing column well (SCW) or the traditional pumping & recharging well (PRW). The inlet water of the PRWFG converges and seeps toward the thermal well both horizontally and longitudinally as combined impacts of the positive recharging pressure, the negative pumping pressure and the gravity. During the procedure of seepage, the heat transfers between the inlet water and the water/solids in the aquifer via conduction, convection and thermal dispersion. The amount of heat transferred directly affects the efficiency and the capacity of the thermal well. Due to the low velocity of underground water, heat conduction occurs between the fluid and the solids, as well as between the solids. The heat transfer coefficient is relatively stable if there are certain hydrogeological conditions. Heat convection and thermal dispersion occur in the pores among the solids and the heat transfer coefficients depend on the flow rate of groundwater. A small amount of inlet water enters the outlet water pipe after heat exchanged with the gravel zone and the wall of the thermal well. Considering the facts that normally the porosity of the gravel zone is larger than that of the aquifer, the pressure difference between inlet and outlet water pipes is high and the distance between them is short, flow transfixion is more commonly happened in the thermal well than in the aquifer. Flow transfixion is a process that the inlet water in the thermal well enters the outlet water pipe through the gravel zone and the zone near the wellbore. The flow transfixion leads to a thermal transfixion by mixing water at different temperatures and mixed flow moves to the outlet water pipe. The formation of flow/thermal transfixion reduces the heat transfer efficiency and load-carrying capacity of thermal well. Currently, the bleeding strategy is usually used for decreasing flow/thermal transfixion. With the rapid development of computational fluid dynamics, numerical simulation is widely applied to the field of ground source heat pump. However, lots of researches focus on the aspects such as the thermal response radius of the pumping and recharging wells, the effect of groundwater seepage on the ground heat exchangers, and the characteristic of aquifer thermal energy storage. Considering the fact that there is insufficient research to predict the flow/thermal transfixion and the temperature migration of PRWFG, this paper provides a fundamental study in order to better understand the operation mechanism. The dynamic characteristics of PRWFG are quantitatively studied by establishing observation point, lines, surfaces and volumes based on the validated numerical model. The strength of flow transfixion is defined as the portion of the inlet water flow from the thermal well directly enters the outlet-water pipe through the gravel zone. Results show that the resultant velocity of PRWFG inlet water which flows back to the aquifer can be replaced by the component velocity in a specific direction. In this model, the strength of flow transfixion strength is 1.2 %. The time for the thermal transfixion to start and completely developed is 2.5 and 12 minutes respectively for the model running. It is also observed that during the same period when there are severe variations of the outlet water temperature, the thermal transfixion occurs and develops. In the area within 100 mm from the axis of thermal well, where the seepage velocity of groundwater is higher than 1×10-3 m/s, the velocity front migration is faster than the temperature front migration. On the contrary, the temperature front migration is greater than the velocity front migration. The quantitative analysis of flow transfixion, thermal transfixion and temperature front migration of PRWFG will provide a theoretical basis for further exploration of the optimized operation of the PRWFG system with higher efficiency.