中文摘要：

使用2008--2011年沪、深A股上市公司的数据，考察审计市场集中度与审计质量的关系及外部制度环境的调节作用。研究发现，在全样本中，审计市场集中度与审计质量显著负相关，审计市场集中度的提高并未改善审计质量，而且外部制度环境的调节作用并不显著。进一步按照外部制度环境分组检验的结果发现，在制度环境较好的地区，审计市场集中度与审计质量显著负相关，说明外部制度环境的改善可以减弱审计市场集中度对审计质量的负向影响。

英文摘要：

Based on the data of f listed firms in the A-share of Chinese stock market from 2008 to 2011, this paper examines the relationship between the regional audit market concentration and the audit quality as well as the moderating effect of outside institutional environments. The results indicate that the regional audit market concentration is negatively related to the audit quality in the experimental sample of the control group, but the negative moderating effect of such institutional environments is not significant in a better institutional environment. A further study finds a positive relationship between the audit market concentration and the audit quality. Therefore, the result again shows that institutional environment plays a negative regulation role in the above relationship.