We have studied the ordering processes of Ag on Si (111) by LEED using a homemade high re-solution spot profile measuring equipment. The results show that the growth processes of Ag 31/2 domain satisfy scaling symmetry. They are self-similar growth processes. The studies also show that the growth exponent is near 1/2 in the early stage of the growth processes. We propose a growth mechanism of Ag diffusing from Ag(111) islands to form Ag 31/2 domains. This article also suggests a way to obtain perfect surface structures in lower temperature by using light-assisted anneal.