The invention provides a photolithography method and relates to the technical field of semiconductors. The method includes S101) a step of forming a positive photoresist layer and a surface photogradable alkaline layer in order on a membrane layer to be etched, S102) a step of exposing the positive photoresist layer by utilization of a mask, and S103) a step of performing negative development treatment by using an organic solvent to dissolve and remove non-exposure zones so as to form a patterned photoresist. According to the method, the surface photogradable alkaline layer is formed on the positive photoresist layer before the exposing step, thus avoiding T-top issues of the patterned photoresist formed through the negative development treatment.