In order to break through the selection limitation of substrate materials and achieve high imaging quality in the imaging wave band, the imaging diffractive optical elements is introduced to the ultrathin annular aperture imaging system. A hybrid refractive-diffractive ultrathin annular aperture imaging system is designed with four reflection structure, and the results of image quality evaluation and tolerance analysis are given. The substrate material of the hybrid refractive-diffractive ultrathin annular aperture imaging system is polymethyl methacrylate (PMMA), focal length is 35 mm, and effective aperture is 29 mm. The results show that the lateral color aberration is less than 2.2 μm and the Modulation Transfer Function (MTF) is more than 0.4 at the spatial frequency of 166 lp/mm, thus high imaging quality is achieved. The tolerance analysis and thermal analysis of the annular aperture imaging system are given. The MTFs of tangential and sagittal direction are greater than 0.2 for each field of view when the spatial frequency is 166 lp/mm. The MTFs of tangential and sagittal direction are greater than 0.28 for each field of view at 0℃ ~40℃ when the spatial frequency is 166 lp/mm.