中文摘要：

我国会计师事务所规模与审计质量之间是否存在正相关关系，现有研究一直存在争议。本文从注册会计师的执业环境出发，对此进行了重新审视。用上市公司实际控制人的控制权与现金流权之差衡量事务所面临的监管风险，研究发现，大事务所只对监管风险较高的客户提供高质量的审计服务。进一步的研究表明，事务所面临的监管环境改善后，大事务所才对所有客户提供高质量的审计服务，审计质量与事务所规模之间的正相关关系不再依赖监管风险而存在。因此，在法律环境相对薄弱的情况下，加强监管是促使会计师事务所提供高质量审计服务的有效机制。

英文摘要：

Different from the results of studies based on advanced markets, the positive relationship between auditor size and audit quality are not found in most of researches based on China. This paper reviews the relationship between auditor size and audit quality after taking into consideration the supervision risk of audits. We measure supervision risk with the control right and its divergence between cash flow right of ultimate controller of listed firms. We found that bigger auditors provide higher quality audits only to clients with higher supervision risks. Further results show that bigger auditor provide higher quality audits to all clients after supervision risk increases. Our results imply that strengthening supervision from regulators is an efficient alternative institution mechanism for the improvement of audit quality when legal environment is poor.