In order to study the electrostatic field in the flowing medium, the model of metal plate in the laminar flow was built on the basis of the related knowledge of electrochemistry and fluid mechanics, and the analytic expression of corrosion potential based on point charge source in the three-layered media model was deduced by using the expansion of Bessel function and its inverse operation, then the expression of electric field was obtained in the meantime. The corrosion potential of metal plate varying from different flow rates at arbitrary seawater depth was calculated by the listed expression. The simulation result was tested and verified through experiment. The result shows that the model in current density generated in the electrochemical reaction under laminar flow conditions is in better agreement with the experimental data, and the electric field distribution changes with the flow velocity and the length of the laminar flow direction.