The authors investigate the ownership structures about American stock corporations and think that the successful experiences based on institutional arrangements for the ownership structures of American listed companies and the way to carry out ownership authorities will give some following enlightenments for Chinese stock companies to perfect their ownership structures:Let all kinds of equity ownerships tradable completely,some ownership diffused or concentrated should be determined by market.To decentralize and transform the state-owned ownership through in the competitive industries,and the ownerships should be mainly holded among legal investors,strategic investors, individuals,employees,managers,foreign investors. The following results are realized to develop perfect law and regulate systems with the function enhancing fair competition and make ownership structure,corporate governance mechanism,all markets,corporate performance interact profitably.