我國會計師事務所的組織文化與會計師的法律責任及盈餘分配機制有其特殊性，為避免低估審計客戶對會計師之重要性，本研究以事務所內部審計組別作為衡量審計客戶重要性的基礎，探討會計師之審計客戶重要性與盈餘品質之關聯性。其次，過去文獻發現會計師之產業專精程度能抑制管理當局從事盈餘管理，故本研究進一步探討當審計組別會計師在特定產業的專精程度，是否能有效減緩審計客戶重要性對盈餘品質的不利影響。實證結果發現：在控制影響盈餘品質的相關變數後，當審計客戶對特定會計師所屬審計組別的相對重要性越高，該審計客戶的裁決性應計數絕對值越大，顯示會計師之獨立性會受到經濟誘因所衝擊；如以簽證審計客戶的家數作為計算市場占有率的基礎，以衡量審計組別會計師的產業專精程度，則發現會計師之產業專精程度確能有效減緩審計客戶的重要性對盈餘品質的不利影響。本文推論此實證結果係因會計師之產業專精程度乃持續累積同產業之不同公司的審計工作經驗所形成，故以審計組別之簽證審計客戶家數作為衡量產業專精程度的基礎，較能適切評估會計師的產業專精程度對盈餘品質的影響。

This study examines the association between the auditor's client importance and earnings quality. We know that the CPA firms' organizational culture, legal responsibilities and profit sharing mechanism in Taiwan are different from the regulations of developed economic entities. Thus, using the audit groups within a CPA firm to measure the auditor's client importance is more precise in Taiwan. In addition, inspired by previous literature that finds auditor's industry specialization is a mitigating factor of earnings management, we further examine whether auditor's industry specialization based on audit group can effectively reduce the negative impact of client importance on earnings quality. After controlling the influences of earnings quality related variables, the empirical results evidence that: First, the more important a client to a specific audit group, the more absolute value of discretionary accrual of such client. It suggests that auditor's independence is compromised to his/her economic incentives. Second, we observe that the client-number based auditor's industry specialization, which is measured by the number of clients, effectively restrains the harm of client importance on earnings quality. According to this finding, this study infers that the client-number based auditor's industry specialization can effectively measure the mitigation effect of auditor expertise on the negative impact of the client importance on earnings quality.