When considering the influence of audit quality for mandatory rotation, the competence and knowledge of successor auditors should be considered in addition to their independence. That is, the choices of successor auditors who are expected to enhance audit quality for companies that rotate their auditors can be seen as a key factor that affects the efficiency of the mandatory audit rotation. This study use audit partner rotations of listed companies in Taiwan from 2004 to 2009 to explore the effects of mandatory audit rotation on companies' choices of successor auditors. The empirical results suggest that, the successor audit partner choices are different between mandatory and voluntary rotation companies, and mandatory rotation companies are significantly more likely to engage industry specialist to be their successor audit partners to minimize the switching costs of required auditor switches. In addition, compare to voluntarily rotation companies, mandatorily rotation companies are more likely to rotate only audit partners rather than rotating both audit partners and audit firms around mandatory audit rotation periods.