A digital-mask projection lithography (DMPL) technology based on digital micro-mirror device(DMD) is proposed. The femtosecond laser is used as a light source, combining with a high zoom ratio objective lens to shrink the reaction region of photoresist with photons. By adjusting the light field distribution, the spatial resolution of the DMD projection lithography is improved to submicron, and maskless projection lithography with a cross-scale processing capability (a single exposure area of over 100 μ m and an exposure accuracy of hundreds nanometers) is realized. Detailed analysis of the geometry and physical optics models is studied theoretically. The relationship between the number of pixels and the size of the processing structure are clarified. The key technical issues of limited resolution in DMPL are investigated based on the physical optics model.