Abstract: A 3-DOF robot arm design is presented for the Captive Trajectory Simulation (CTS) test in the FL-12 wind tunnel. It is an integrated mechatronics device. The paper introduces its transmission principle design, physical design, control system design, drive element selection calculation and verification, then verifies the design results with dynamical and static mechanics analysis. The results show that the device improves the load in pitch and yaw from 100Nm to 250Nm with control precision from 0.1°to 0.05°, and also improves the load in roll from 10Nm to 20Nm with control precision from 0.1°to 0.05°.The structure of drive element and cable, fairing configuration, overall dimension are optimized to make the device more suitable for the wind tunnel test.