Aerodynamic testing plays an important role in evaluating the design method and optimizing the significant system characteristic parameters of flapping-wing vehicles. This article presents a newly developed three-dimensional force sensor with simple structure, low cost and high performance, which is used in the aerodynamic testing system of flapping-wing vehicles. It focuses on the design and calibration method of the three-dimensional force sensor. Firstly, the feasibility of the structure design is verified by the model of the micro-variation kinematics of the elastic mechanism. Then, the decoupling calibration experiment of the sensor shows that the nonlinear error of the sensor is smaller than 1. 19% , the coupling error is smaller than 3. 21% , and the sensitivity is larger than 1. 1 V/ N. Finally, by testing the aerodynamic force of a small flapping-wing vehicle, the quantitative evaluation data of the main wing aerodynamic force of the flapping-wing vehicle with the influence of the parameters are obtained, which can provide an effective help for the vehicle to achieve indoor and outdoor maneuverable flight.