Abstract：The paper discusses the formation and regional structure development of the key settlement pattern above county level in Guanzhong Area. It points out that the real formation of key set tlement pattern in Guanzhong Area was marked by the county system practised by Qin dynasty, and this pattern had formed completely a two levels system including the primary city and county level settlements until the unification of Qin Dynasty. From East Han Dynasty on, rank structure of key settlements in Guanzhong Area developed gradually from two levels to three levels; in spatial distribution, the key settlement pattern show changes from concentration along Weihe River to political regional balance, and changes to the industrial and commercial city after Tang Dynasty. Also, being the primary city, Xi'an (Chang'an) had changed in the regional structure, of which the most notable was the oppsite change in spatial site of political power core and market area.
