Abstract: In order to characterize wavefront aberration behavior of misaligned reflective optical systems over the entire image plane, thereby realize effective alignment to reflective optical systems, the third order coma and third order astigmatism of several reflective optical systems with tilt and decentration were studied. Firstly, the vector form of the third order wavefront aberration of misaligned optical system was deduced. Then, the distribution characteristics of third order coma and third order astigmatism of misaligned classical Cassegrain systems, Ritchey-Chrtien systems and three mirror astigmatism systems in the image plane were analyzed. Finally, the alignment of two mirror and three mirror optical systems was briefly discussed. Moreover, Zernike polynominals were used to fit wavefront aberrations of grid sampling points in the view of field. Third order coma and third order astigmatism were separated and displayed over the whole field of view. Theorectical analysis and practical fitting results were similar, which shows that conclusions are correct.