A method for manufacturing a small-size fin-shaped structure, comprising: forming a first mask layer and a second mask layer on a substrate in sequence; etching the first mask layer and the second mask layer to form a hard mask pattern, wherein a second mask layer pattern is wider than a first mask layer pattern; eliminating the second mask layer pattern; and performing a dry etching of the substrate by taking the first mask layer pattern as a mask, so as to form a fin-shaped structure. According to the method for manufacturing a small-size fin-shaped structure of the present invention, firstly a large-size hard mask is prepared, then a width controllable small-size hard mask is prepared through a wet corrosion, and finally the bulk silicon wafer is etched, so as to obtain the required small-size fin-shaped structure, thereby improving the electrical properties and the integration level of the device, simplifying the processes and reducing the cost.