中文摘要：

本文使用2008-2011年中国沪深A股上市公司的数据，实证检验了省级层面的审计市场集中度与审计收费和非标准审计意见之间的关系。研究结果发现，中国审计市场集中度对审计收费的影响具有区域异质性，在东部地区，审计市场集中度与审计收费正相关，在中西部地区两者则呈负相关关系。在全样本和东部地区中，审计市场集中度越高，审计师出具非标准审计意见的可能性越低，这一负向关系在中西部地区不显著。本文的研究有助于加深理解中国审计市场结构、审计收费和审计师独立性之间的关系。

英文摘要：

It＇s different from the United States or other developed countries in which the vast majority of public firms are audited by the Big4 auditor, China＇s audit market includes a large number of small domestic audit firms. A CPA firm merger wave, however, was activa- ted by the government and Chinese CPA Association since 2007. Audit market structure in China has changed enormously since that merger wave. It is meaningful for us to analyze effects of such changes in the market structure to the market performance. Previous research indicates that the audit markets are local. Therefore, we focus on local audit markets in China to examine the effects of audit market concentration on audit fees and auditor independence. To assess audit market concentration, we follow the approach of Boone et al. （2012） to calculate the Herfindahl Index （HI） for each year based on audit fees in the province market. We proxy auditor independence by auditors＇ propensity to issue modified au- dit opinions （MAOs）. Our sample covers the 2008--2011 period to avoid the potentially confounding effects of the CPA firm merger wave and the adoption of new accounting standards in 2007. The results indicate that the relation between audit concentration and audit fees is regional heterogeneity. We find evidence of a positive relationship between audit concentration and audit fees in eastern area but a negative relation in central and western regions. As for MAOs, it shows in the paper that the higher concentration in the eastern area is associated with lower possibilities for auditors to give MAOs, and the relation is not significant in the central and western regions. It suggests that the audit concentration does not improve auditors＇ independence in China. Our results are robust after a series of robustness tests. Our study is important because it adds to current work examining the effects of audit market concentration. And we provide evidence of the relationship between the local audit market structure and market performance i