Direct laser writing (DLW) technology usually fabricates micronanostructures based on the principle of two-photon polymerization. However, two-photon polymerization requires high laser intensity which can be achieved by expensive femtosecond lasers. To address the issue, a direct laser writing method has been proposed in this work; it is based on triplet up-conversion which is characterized by its low cost, high precision, multidimensional property, and rapid processing. The feasibility of this method is jointly verified by applying both dynamic modeling and experiments. Based on the obtained results, the low laser intensity fabrication of multidimensional nanostructures is achieved. The minimum line width (∼50 nm) of micronanostructures is reached when the laser intensity is set at 2.5 × 105 W/cm2 along with a processing speed of 150 μm/s. As a result, the direct laser writing method, based on triplet up-conversion, offers a new route to achieve low-intensity and high-precision micronanostructure fabrication.