The six-point spatial angle measurement method is proposed in this paper.Six ta rgets are attached on the measuring joint,whose 3D center coordinates can be reconstructed by stereo vision method.Firstly,hydra ulic pressure fluctuation correction is implemented.Then the actual rotate angle is calculated.The simulation res ults show that the proposed six-point measurement method is effective to eliminate the influence of pressur e fluctuation while measuring the rotation angle of joints.The projection method applied for calculation of spati al angle whose measurement error is about 0.037° if error of spatial p oints is within (－2,2) mm,is better than the unit quaternion method. Finally the actual measurement for an underwater manipulator driven by hydraulic power verifies the feasibility of the proposed measurement method.