本研究主要係探討會計師任期及事務所任期愈長是否可提升市場效率以減緩資訊不對稱。在無效率之市場下，資訊無法有效反應於市場，此時存在資訊不對稱之問題，則需要政府透過對審計人員執行強制輪調以保護投資人；在有效率之市場下，資訊已充分反應於市場，則不需政府干預以保護投資人。本研究結果發現，無論會計師任期或會計師事務所任期愈長皆可提升市場之效率，而綜合兩種審計任期之效果，事務所任期顯著能提升市場之效率，而會計師任期對提升市場效率已不顯著。;Our study explores whether longer audit tenure can promote the market efficiency to reduce information asymmetry. Under an inefficient market, information cannot response effectively to the market, which causes a problem of information asymmetry. Therefore, it requires the government to protect investors through the enforcement of mandatory auditor rotation policy. On the other hand, under an efficient market, information has been fully reacted in the market, so interventions from government are unnecessary. There are two findings in our research. First, we find that the longer the audit tenure is, the more the efficiency of the market can be improved. Second, with the comprehensive effect of the two kinds of audit tenure, audit firm tenure can significantly improve the efficiency of the market, while the effect that audit-partner tenure can improve the efficiency of the market is insignificant.