Taking the Manwan Reservoir continent beach of Lancang River as the research object, during reservoir operation, water level and temperature was real-time monitored. The infiltration flow velocity was calculated by hydrodynamic method and temperature tracer method according to the data of water level and temperature. The results show that the Hatch phase method has higher accuracy in calculating the subsurface flow exchange caused by the water level fluctuations in the reservoir area, the flow exchange velocity ranged from -5.87 × 10-5 m/s to 12.92 × 10-5 m/s, and the hyporheic exchange volume is 2.66 m3 during the monitoring period. The results of Hatch phase method lagged behind hydrodynamic method when calculating peak flow velocities. The velocities decreased with the increase of the depth in island, and the curves of flow velocities at different depths are similar.