In order to realize the accurate position of an off-axis aspheric surface in optical alignment, it is necessary to strictly control the six degrees of freedom, especially the two degrees of freedom that affect lateral displacement and tilts angle. But it′s very difficult to obtain the above two accurate values using general off-axis aspheric surface measurement technique, so it′s same difficult to realize its precise alignment. The article introduces a new method that applying the close relationship between the center image of radius of curvature and the optical axis of the self-regulating instrument, and by using the precise measurement, the purpose of measuring lateral displacement and tilts angle is achieved. Experiments show that the error of lateral displacement is less than 0.05 mm, the error of tilts angle is less than 10″, and the wave aberration root mean square is equal to 0.02λ (λ=632.8 nm). It can obtain the perfect image and realize the precise alignment of the off-axis aspheric mirror by using this method.