Abstract: Based on the vector wavefront aber ration theory, the misalignment induced aberration's characteristic of TMA optical system was analyses in this paper. It is shown that a misaligned TMA has three residual 3rd aberrations. The 3rd order spherical aberration that is constant over the field and the 3rd order coma is a constant in magnitude and orientation over the field. Moreover, the 3rd order astigmatism is field-asymmetric in orientation and increases linearly with the field, and the location zero for the field-asymmetric, field linear astigmatism always reside at the center of the field of view. It has been demonstrated that a TMA under assembly is only measured to have perfect performance on-axis which is not aligned in any significant way, so the measurements of multiple field points for the TMA are required in the process of alignment. Under condition of remove axial coma, if astigmatism is measured on-axis, which is caused by the primary mirror astigmatic figure error but not the misalignment.