中文摘要：

以2003～2005年沪深两市A股为样本，以上市公司会计盈余质量为衡量中小投资者保护水平的指标，采用非均衡面板分析方法，实证检验了中国资本市场中机构持股对中小投资者保护的影响。结果显示，在样本期间和范围内，无论是在应计质量还是盈余及时性方面，机构持股降低了会计盈余质量，没有发挥保护中小投资者的作用。此外，股权集中降低了上市公司会计应计质量。上述研究发现对理解发展机构投资者的经济后果及其发挥不同作用的制度条件具有重要的意义，也为投资者保护研究提供了一个有益的视角.

英文摘要：

Taking accounting earnings quality as the index of investor protection,the paper uses unbalance panel date research method, the effect of institutional ownership to investor protection is tested with the data of companies listed in Shanghai Stock Exchange and Shenzhen Stock Exchange from 2003-2005. The result shows that, no matter from the persistence of transitory loss components in earnings or accrual quality, institutional ownership reduces the accounting earnings quality and does not protect the interest of minority investors. The result also shows the ownership concentration may reduce the accounting accrual quality. The findings are very important to understand economic consequences of developing institutional investor and the institutional conditions of its taking effect,and also offer a useful perspective for investor protection study.