中文摘要：

我国《关于证券期货审计业务签字注册会计师定期轮换的规定》要求签字注册会计师以五年为限进行强制轮换，旨在通过限制审计师与客户之间的“亲密联系”，有效提高上市公司的审计质量。本文基于这一制度背景，研究了签字注册会计师任期及其强制轮换对上市公司审计质量的影响。实证发现：签字会计师任期的延长与审计质量的关系显著受到客户公司与事务所经济依存度的影响，在会计师事务所经济重要程度较低的客户公司中，签字会计师任期的延长显著降低了审计质量；而在事务所经济重要程度较高的客户公司中，任期与审计质量的关系则并不明确；同时，上市公司在执行《轮换规定》要求的签字注册会计师更替后，审计质量并未得到显著改善。基于此，本文研究认为，尽管我国《轮换规定》的出台实施十分必要，但现有《轮换规定》细则对上市公司审计质量的提高并不完善，《轮换规定》应该选择在会计师事务所和签字注册会计师两个层面对审计单位的强制轮换提出更细致的要求。

英文摘要：

After the issue of CPA mandatory rotation had been provided by U. S inSarbanes Oxley rulers, Great importance has been attached to the relationship between CPA tenure and audit quality. China Securities Regulatory Commission and Ministry of Finance promulgated the Regulation on the Auditor Rotation of the CPAs Having the Qualification of Auditing Securities and Futures, in which signature CPA is asked to keep auditing a certain company at most five years. Based on the regulation that a certified public accountant can audit a firm for at most 5 consecutive years, this paper studies how a certified public accountant＇s tenure and rotate affect audit quality of Chinese listed firms. The results can provide empirical evidence for the effect of this regulation. We found that the audit tenure of CPAs is significantly negative related with audit quali- ty. And this phenomenon mainly exists in the companies that are of less economic importance for the audit firms by which the CPAs are employed. These.results illustrate the necessity of the Rotation Regulation. However, after the listed firms change the CPA who has audited the firm for 5 consecutive years, the accounting information of the listed firms does not become more conservative. This result shows that Rotation Regulation does not have effect to improve the audit quality. It illustrates that Rotation Regulation requests the listed firm to change the CPAs who provide audit service cor the firm for 5 consecutive years, but this rota- tion happens to the CPAs in a same audit firm. The successor employed by the same audit firms cannot improve auditing standard and auditing independence. And the auditing quality for client firms does not improve significantly. So the effect of Rotation Regulation is weak- ened at last. These findings supply empirical support for the improvement of the regulation. Rotation Regulation should require both CPA and audit firms to rotate at the same time.