本研究主要探討會計師客戶集中度與於審計品質之關係，實證結果發現異常應計數與客戶集中度呈現顯著正相關，另外，更進一步發現異常應計數與客戶集中度呈現顯著相關的現象主要發生在會計師的相對非重要客戶上。上述實證結果支持本研究之假說，客戶集中度與審計品質為負向關係。鑒於會計師的客戶集中度越高，代表其客戶重要性差異越懸殊，在考量審計失敗及聲譽損失的風險下，會計師主要資源會挹注在重要客戶，導致資源配置扭曲，降低對於非重要客戶的審計品質，並造成會計師整體審計品質的受損。本研究結果亦提供會計師事務所分配業務及主管機關監督會計師執行審計業務之考量。

This thesis mainly discusses the relationship between accountant customer concentration and audit quality. The empirical results show that abnormal accruals are significantly positively correlated with customer concentration. In addition, the results further revealed that the phenomena of abnormal accruals and customer concentration are significantly related to non-important customers of the accountants. The above empirical findings support the hypothesis that the relationship between customer concentration and audit quality is negative. Under the risk of audit failure and loss of reputation, the major resources of the accountants will be focused on their important customers, which leads to distorted resource allocation. This distortion of resource allocation reduces the audit quality for non-important customers, and reduces the auditor’s overall audit quality.

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