The structures and electronic properties of the SiAun (n = 17-20) clusters are systematically investigated using DFT calculations. The result shows that doping with silicon would significantly change the structures of the gold clusters. For the SiAun (n = 17-20) clusters, the lowest-energy structures exhibit shell-like cage configuration in which the dopant Si atom binds to the cage surface and one Au atom skips to the top of the Si atom forming a SiAu5 or SiAu6 subunit except SiAu19, which is a tetrahedron-like structure with a protruding Au atom. The Au atoms of the SiAun (n = 17-20) clusters carry different partial charges due to their different locations.