Determining pose parameters for space target based on optical sensors and computer vision theory is full of both practical value and theoretical significance. An efficient point-based pose estimation algorithm is proposed to improve the precision and real-time ability of the pose estimation system. In our method, we first get the initial value for target pose through the classical Perspective-3-Point (P3P) method, then introduce the Orthogonal Iteration (OI) optimization method to make a accurate solutions. This pose estimation approach can be applied in any situation with feature points non-coplanar and the number larger than three. Practical experimental results indicate that when the feature point number is up to eight, the RMS error is less than 3 milliradian (0.17°) and the refresh rate achieves 200 frame/s.