In the latest 20 years, x-ray imaging technology has developed fast in order to meet the need of x-ray photo-etching, spatial exploration technology, high-energy physics, procedure diagnosis of inertial confinement fusion (ICF) et al. Since refractive index of materials in the x-ray region is lower than 1, and x-ray is strongly absorbed by materials, it is very difficult to image objects in the x-ray region. Conventional imaging methods are hardly suitable to x-ray range. In general, grazing reflective imaging and coding aperture imaging methods have been adopted more and more. In this paper, according to user’s requirement, we have designed a non-coaxial grazing KBA microscope. The microscope consists of two sets of perpendicular spherical mirrors, each set includes two parallel mirrors. Taking it as an example, we have compiled an optical computing program for the non-coaxial grazing imaging systems so as to analyze and evaluate aberrations of KBA microscope. Thus it can help us to get an optimal comprehension of KBA x-ray imaging system. In the same time, the analytical results provide reliable foundation for evaluating imaging quality of KBA microscope.