A method for detecting molecular is related. The method includes providing a sample, in which a sample surface is distributed with analyte molecules; providing a carrier including a substrate, a middle layer and a metal layer, in which the middle layer is sandwiched between the substrate and the metal layer, the middle layer includes a base and a patterned bulge on a surface of the base, the patterned bulge includes a plurality of strip-shaped bulges intersected with each other to form a net and define a number of holes, and the metal layer is on the patterned bulge; placing the carrier on the sample surface to make the metal layer being attached to the sample surface, in which parts of the analyte molecules are formed on the metal layer; detecting the analyte molecules on the metal layer with a detector.