中文摘要：

本文以审计师对财务重述公司出具严厉审计意见的可能性衡量审计质量，检验客户重要性与审计质量的关系。在此基础上，以财务重述的原因衡量客户的风险性质，进一步考察其是否会对客户重要性与审计质量的关系产生显著的影响。实证结果表明：总体而言，客户重要性水平越高，审计师越不倾向于对财务重述公司出具严厉审计意见；然而，随着客户风险性，贡严重程度的提高，客户重要性与审计师对财务重述公司出具严厉审计意见的可能性由负相关转变为不相关。这些结果表明，客户重要性与审计质量的关系不仅取决于宏观的制度环境，还受到客户的风险微观环境的影响。本文为客户重要性与审计质量的关系提供了新的经验证据和理论解释。

英文摘要：

The main purpose of this paper is to test the relationship between client importance and audit quality and how the nature of client risk affects their relationship. We find that auditors are more inclined to issue severe opinion for financial restatement companies as client importance increases. However, when we distinguish the nature of client risk by the inner causes of financial restatement, we find that the negative relationship between client importance and severe opinion for financial restatement companies diminish. The findings suggest that the relationship between client importance and audit quality is not only affected by macroscopic institution environment, but also depend on microscopic risk environment of clients. This paper provides new empirical evidence and theoretical explanation for the relationship between client importance and audit quality.