As a non-contact and three-dimensional mirror surface measurement method, stereo deflectometry has developed rapidly in recent years. In order to solve the problem that it is difficult to measure large inclination surface with traditional stereo deflectometry, the three-dimensional stitching of stereo deflectometry based on marker is proposed. In this method, the three-dimensional point cloud in the sub-regions under different perspectives was measured by stereo deflectometry. Meanwhile, the three-dimensional coordinates of the markers on the sample table were measured by binocular stereo vision. The markers coordinates were used for coarse stitching, and the ICP algorithm was used for fine stitching. A three-dimensional stitching measurement system is actually built, and a smooth convex spherical reflector with an inclination angle of 25.8 degrees is measured. After stitching, the spherical fitting error is within 3μm. The experimental results verify the feasibility of the method, which is of reference significance for the application of the stereo deflectometry to the three-dimensional measurement of complex optical surfaces with large aperture and large inclination.