A general relationship of three-dimensional-two-dimensional (3D-2D) object image mapping of line vector is proposed to solve the common adaptation problem of optical pose processing of typical rigid targets (mostly with linear externalization characteristics) in the shooting range. The pose information is then obtained by choosing a line vector for object image direction mapping and matching. First, the linear vector of the target body is rotated, the theoretical correspondence between the line vector of the key subject and the calculated pose angle is obtained, and then the key vector is projected to the determined image plane, the mapping relationship between the spatial line vector and the image of the projected image plane is established for the first time, and the spatial line vector is reconstructed using the substation mapping results, in order to achieve the purpose of closed-loop verification of the correctness of the mapping results. The pure direction pose is solved using the significant line vector 3D-2D pose mapping relationship presented in this paper for optical pose processing based on line vector. Especially in the process of occlusion and transformation in the medium and long-term dynamic target attitude measurement, it has good adaptability. Compared with the existing pose processing results, the correctness and reliability of the algorithm are verified.