X-ray imaging technology has developed fast in spatial explorations. In order to obtain higher throughput and larger effective area, Wolter-Ⅰnested telescope structure is usually adopted to focus and image the spatial Xray sources. Traditional optical analysis software is imperfect in the analysis of grazing incident system. Therefore, programs are written using the MT_RAYOR tools to evaluate the image quality of Wolter X-ray nested telescope. MT_RAYOR has an advantage of being general, accurate, convenient and fast in predicting grazing incident Wolter- Ⅰnested structures. Based on MT_RAYOR, the structure parameters of nested conical telescope working at 0.2~ 20 keV are designed, and detailed image quality analysis are presented, including the effective area, point spread function, and encircled energy function. The system can achieve a stable effective area of about 500 cm2 at 0.2~10 keV, and the effective area keeps above 250 cm2 in hard X-ray region, thus, the system has a wide range of working wavelength and good stability. Furthermore, the spokes and surface deformation profile are taken into consideration in order to evaluate the effects on image quality. The results have directive significance to optimization and assembling of the telescope system.