This paper empirically analyzes the effect of corporate governance quality & disclosure quality on the relation between internal specialists of accounting practice and disclosure on preliminary-actual earnings differences. It was analyzed with actual proof through regression analysis regarding preliminary-actual earnings differences as dependent variable and interaction between corporate governance quality (and disclosure quality) and a dummy variable standing for Internal specialists of accounting practice and disclosure as independent variables. The sample consists of non-banking firms with december fiscal year listed in Korean Stock Exchange over 2004-2008. Empirical findings are summarized as follows; There is significant negative association between preliminary-actual earnings differences and hiring specialists of accounting practice and disclosure. And there is significant positive association between preliminary-actual earnings differences and hiring specialists of accounting practice and disclosure in high corporate governance quality (high disclosure quality). This result provides a deeper understanding on corporate governance quality(and high disclosure quality) as internal environment factor and contributes to the decision-makings of interested parties.