In order to improve the joint assembly accuracy of large space deployment mechanisms such as deployment arms, a high-precision and multi-free automatic attitude adjustment system is designed. A measurement system composed of four theodolites and two cube mirrors is used to obtain the spatial pose data of the adjusted joint; Pose adjustment of joint pitch, rotation, yaw, Z vertical lift, Y longitudinal displacement, X lateral displacement through a six-degree-of-freedom parallel mechanism; Complete control of the overall system by designing central integrated software; The six-free posture adjustment of the joints is completed through the closed-loop method of coarse adjustment-fine adjustment-judgment-fine adjustment, so that the final deployment accuracy of the deployed arm meets the corresponding requirements.