A selector for a bipolar resistive random access memory and a method for fabricating the selector are provided. The method includes: providing a substrate; forming a lower electrode on the substrate, where the lower electrode is made of a metal, and the metal is made up of metal atoms which diffuse under an annealing condition of below 400° C.; forming a first metal oxide layer on the lower electrode; performing an annealing process on the first metal oxide layer to make the metal atoms in the lower electrode diffuse into the first metal oxide layer to form a first metal oxide layer doped with metal atoms; forming a second metal oxide layer on the first metal oxide layer doped with metal atoms; forming an upper electrode layer on the second metal oxide layer; and patterning the upper electrode layer to form an upper electrode.