The present invention discloses a method for fabricating a semiconductor nano circular ring. In the method, firstly, a positive photoresist is coated on a semiconductor substrate, then the photoresist is exposed by using a circular mask with a micrometer-sized diameter to obtain the circular ring-shaped photoresist, based on the poisson diffraction principle. Then, a plasma etching is performed on the substrate under a protection of the circular ring-shaped photoresist to form a circular ring-shaped structure with a nano-sized wall thickness on a surface of the substrate. The embodiment of present invention fabricates a nano-sized circular ring-shaped structure by using a micrometer-sized lithography equipment and a micrometer-sized circular mask, and overcomes the dependence on advanced technologies, so as to effectively reduce the fabrication cost of the circular ring-shaped nano structure.