Recently,the collective phenomena emerging from the interactions of individuals in social systems,such as the avalanches of epidemic,the formation and synchronization of opinion,has attracted an increasing interest of physicists.Many empirical works show that social systems share some universal characteristics such as the smallworld effect and the power scaling degree distribution.An obvious question is how those features affect the collective phenomena in social systems.Here,the opinion formation on complex networks was focused on and previous investigations on the three famous opinion models were reviewed.