For the purpose of fabricating large aperture, light-weighted, and high efficiency diffractive elements, the design of microstructure and fabrication technology of diffractive Fresnel membrane elements were proposed. A 4-step diffractive membrane with 320 mm diameter and F/#100 was designed by Zemax software. The continuous phase distribution was transformed into discrete steps by Matlab software. The fabrication processing chain of membrane diffractive element was studied. Using polyimide film as membrane material and fused silica as substrate, the PI membrane with thickness of 20 μm was fabricated through multi-times spin-coating. The mechanical structure of membrane fixture was designed by using Solidworks software. The measurement results of corresponding position of membrane and glass substrate show that line width errors is less than 1.3%, and the step depth errors is less than 8.6%. The diffraction efficiency in wavelength of 632.8 nm is 71.5%, which is 88% of theoretical value. It can be concluded that the membrane has light weighted structure, high replicated accuracy, and high diffraction efficiency, which meets the requirement of space-based telescope.