For the existing binocular position and attitude measurement system with only two target points, it is impossible to use additional calibration objects to calibrate the two cameras without a common field of view. In this study, a calibration method for a binocular camera without changing the system struc. ture and instead directly using the existing equipment was proposed. First, the relative position between the two camera coordinate systems and the common coordinate system was fixed, and multiple sets of co. ordinate data were acquired by moving the calibrator several times. An improved algorithm based on a di. rect linear transformation(DLT)method was used to optimize the relative transformation from each cam. era coordinate system to the common coordinate system. Finally, the relative conversion between the two camera coordinate systems was obtained using the optimized relative conversion from each camera coordi. nate system to the common coordinate system. The distance between the two target points could be ob. tained using the relative conversion between the two camera coordinate systems, and this distance was se. lected as the evaluation index of the calibration accuracy. The experimental results show that the mean square error of the distance between the target points obtained using this method is less than 0. 2 mm, which meets the practical application requirements.