In this study, a digital micromirror device (DMD) maskless lithography technique, combined with femtosecond laser source and large-area splicing method, was used to rapidly fabricate a large-area micro/nanostructure with high resolution and millimeter size. Moreover, the edge roughness of the structure introduced by the uneven distribution of the light field energy is improved by single optical field line scanning. This would greatly decrease the edge roughness of the line and effectively control the accuracy of the structure. In this study, positive photoresist commonly used in the semiconductor field was the main research object, and the rapid fabrications of 1 μm equidistant line arrays with an area of 7.4 mm ² and 10 μm equidistant line arrays with an area of 38.7 mm ² were achieved. This study provides a new method for the fabrication of large-area micro/nanostructures which can be applied in the fields of gas-liquid flow, drug transport, and crystal growth.