Maskless lithography based on spatial light modulators is an important development direction of lithography technology. In recent years， with the improvement in digital micromirror device （DMD） chip integration and performance， maskless lithography based on DMD has become the main digital lithography technology. By virtue of a programmable digital mask that can be gray-scale modulated to replace the prefabricated physical photomask used in traditional lithography， it can greatly simplify the process of lithography and improve the flexibility of lithography. It is widely used in many research fields including planar micro-nano devices， metamaterials， microfluidic device chips， and tissue biology. Starting from the principle of maskless lithography， we briefly introduce the structure of uniform illumination system and miniature projection system， and then summarize the development of spatial resolution enhancement technology for traditional planar lithography， grayscale lithography， and three-dimensional micro-stereolithography technology. Finally， we highlight the typical applications of digital maskless lithography and propose its future development direction.