In wide linear-field of view, large relative aperture mirror system, it is unavoidable to use high order aspheric surfaces. In this paper the design of the compensators for testing the secondary and the tertiary mirror of a 3 mirror system is described. The surfaces under testing have high order up to r16. The diameter of the secondary is 112 mm, radius of curvature is 211.462 mm, and the conic constant is 0.07744075. The diameter of the tertiary is 272 mm, radius of curvature is 197.722 mm, and the conic constant is 0.2623604. Three elements and four elements compensators have been designed. The residual aspherical aberration has been minimized to about λ/20.