In the latest 20 years, X-ray imaging technology has developed fast in order to meet the need of X-ray photo-etching, space exploration technology, high-energy physics, procedure diagnosis of inertial confinement fusion (ICF) etc. However, conventional imaging methods are hardly suitable to X-ray range, grazing reflective imaging and coding aperture imaging methods have been adopted more and more. KBA X-ray microscope is grazing non-coaxial incident X-ray microscope, and four mirrors distribute spatially. The front pair is not perpendicular to the back pair strictly, but tilts a small angle along the ray, and it brings very large difficulty to analysis of image quality. Thus general optical CAD program is not suitable to this kind of optical system. In this paper, programming for non-coaxial grazing incident microscope is discussed in detail, and it is used to analyze the synthesis errors. When the tolerance of object distance is between -0.4～+1 mm, the tolerance of grazing incident angle is between -8″～0, and the tolerance of angle between the bimirror is within -20″～0, the blur is permitted.