本研究之研究目的在探討我國會計師、事務所任期對盈餘品質的影響，是否與美國不同，並一併就我國以第五年作為會計師輪調期限是否影響盈餘品質進行研究。在內生變數方面，以往研究多以裁決性應計數和流動性應計數作為盈餘品質的參數，本研究則跟隨Ho, Liu and Thomas(2007)之研究，採企業實際盈餘和分析師預測盈餘之差異作為盈餘品質的參數，比較美、台之研究結果異同。 研究結果發現，以裁決性應計數絕對值作為盈餘品質參數時，盈餘品質與會計師、事務所任期長短均具有顯著正相關，即會計師、事務所簽證任期越長，盈餘品質越高。然以企業報導盈餘和分析師預測盈餘之差異作為盈餘品質的參數時，卻出現事務所任期長短與盈餘品質呈顯著負相關的結果。此結果”似乎”與Ho et al. (2007)研究結論相似。推測可能原因有二，一是公司在與事務所長期合作後，本質上改變了公司的營運績效，進而提升了盈餘品質使公司可達成或超越分析師預測，另一原因則如Ho et al. (2007)所提出，事務所任期越長越可能引導分析師調降對公司的盈餘預測。至於我國會計師的輪調期限，就本研究所得出的結果推論其效益可能不顯著。 This study examines the influence between the auditor/audit firm tenure and earnings quality. At the same time, the study discusses if the mandatory auditor rotation rules were properly. We use not only abnormal accruals and current accruals as proxies for audit quality, but following Ho, Liu and Thomas(2007) to use earnings surprise (report earnings in excess of analysts’ projections) as a proxy for audit quality. We hope by using different samples from America to find if there is any diversity. Our empirical result shows that the firms with longer auditor/audit firm tenure are more likely to have higher earnings quality when we using abnormal accruals as a proxy for audit quality. Nonetheless, when using earnings surprise as a proxy for audit quality the firms with longer audit firm tenure are more likely to have lower earnings quality. The result is “almost” the same with the consequence of Ho et al. (2007). We infer there are probably two reasons. One is the company substantially advancing its financial status. The other one similar to the consequence of Ho et al. (2007) is that the firms with longer audit firm tenure are more likely to guide analysts’ forecasts downward. As to the mandatory auditor rotation rules are properly or not. The results show that it is less likely to reveal the rules’ benefit.