Abstract: Based on the similarity between the electric potential differential control equations of the current field and velocity potential differential control equations of the seepage field, the flow field method(FFM) can not only determine the seepage by measuring the distribution of current field, but also can efficiently figure out the leakage location of the dam. For further discovering the vector distribution and direction of seepage more accurately, the horizontal and vertical potential difference between the upstream and the downstream can be measured to simulate the vector distribution of seepage. In this paper, we illustrate the principle of vector flow field method(VFFM) to simulate the vector distribution of seepage from the aspects of current density, potential differential and absolute value of potential differential. The verification experiment is carried out in a case study of earth-rock dam seepage detection. The results demonstrate that the VFFM can effectively discover the seepage grade and leakage direction. Combined with the results of FFM and VFFM, the proposed method can provide a new solution for detecting the leakage location, seepage grade and leakage direction of earth-rock dam.