Groundwater seepage can improve the heat transfer performance of borehole ground heat exchanger (BGHE), and the corresponding velocity is the significant parameter which shows the degree of seepage role. The paper presents the mathematical model while groundwater flows through BGHE, and the comparisons between pure conduction and the combined heat transfer including conduction and convection are made. Points are set around borehole to test the temperature response at different time and then the goal functions containing both model results and test results are established. Next, the back calculation method is employed to obtain the value and orientation of velocity and therefore the convection role can be expressed. The reasonable points' locations along both depth and radial directions are analyzed; the comparisons of points' temperature responses are made according to the variation of seepage orientation and value. The relativity between points' locations and velocity value is discussed to make the calculation result acceptable. In addition, a number of trials are made to check the validity of back calculation method. The temperature response curves of points are shown and the characteristics embodied are investigated. Accordingly, the finite line heat source seepage model is significant to realize groundwater velocity. (C) 2016 Elsevier Ltd. All rights reserved.