This paper describes a design study of the KAO (Korea Astronomy Observatory) 1m telescope. The telescope uses an F/2.7 zerodur primary mirror which has a double arch back contour shape. For the zenith pointing, the primary mirror is to be held by a 6-point axial support system at the back surface. For Horizon, a 3-lateral support system is to be designed and located at the center of gravity of the mirror. In this paper, a parametric design study of a double arch back contour shape is to be performed to meet an optical surface deflection requirement, a surface RMS wavefront error of (lambda) divided by 10, using the finite element program, ANSYS, for the mechanical surface deformation, and the PCFRINGE program for the evaluation of the optical performance. Additionally, the static and modal frequency analysis of the truss structure and yoke were performed.