In this paper, structural and electronic properties of zigzag single-walled boron nitride nanotubes are investigated within density functional theory by adding one gold atom as an impurity. One boron and one nitrogen atoms are substituted by one gold atom separately. Calculations show that the substitution of Au atom on boron atom turns the BNNT into a p-type semiconductor with a band gap of 2.435 eV. On the other hand, doping the Au atom on N site diminishes the pristine BNNT gap to 3.905 eV.