The present disclosure pertains to a photolithography method based on bilayer photoresist, the method including applying one layer of positive photoresist on a substrate and drying, then applying one layer of negative photoresist on the positive photoresist and drying; exposing the two layers of photoresist using a photolithography mask with mask patterns or through focused direct write under a source of exposure, and then drying; developing, with developer for negative photoresist, the negative photoresist; controllably developing, with developer for positive photoresist, the positive photoresist; forming patterns on the material of the substrate through material deposition technology or etching technology; removing the photoresist. Compared with existing single-exposure photolithography technology, the method of the present disclosure is simple and a line width smaller than that of the conventional technology can be achieved by pattern contouring. The method can be widely used in semiconductor process and has extensive values of research and application.