In order to solve the accuracy problem of pose measurement of space target based on three linear array CCD, we propose a high precision pose calculation method. This algorithm integrates all linear array CCD camera coordinate systems. The improved orthogonal iterative algorithm is used to solve the pose parameters by establishing a new error evaluation function, and the nonlinear optimization is performed subsequently. Simulation and measurement results show that the proposed algorithm effectively avoids the problem of no-convergence or poor convergence caused by data deterioration or initial value selection. Compared with the traditional algorithm, both the measurement accuracy and noise immunity of the proposed algorithm are effectively improved and the computational efficiency is improved by 4.6 times. The maximum relative error of six degree of freedom is 0.71% in actual measurement. The proposed system can realize high precision and real-time measurement of spatial target, which has the advantages of convenient installation and wide applications.