To generate a tiny and steady force for the calibration of the ocean current sensor, a force-reduction mechanism has been performed in this paper. The paper focuses on the whole process of this mechanism based on the flexible hinges from the working principle, parameter determination to FEM simulation and so forth. By analyzing the relationship between reduction multiple and structural parameters of the levers and hinges, material and geometric dimension are chosen reasonably. Finally, applicability of the choice of the mechanism is verified through finite element analysis. The simulation results show that using this mechanism the input force can reduce to required force of µN for the calibration.