This paper examines the impact of new Chinese Accounting Standards (CAS) adoption on audit fees. Since Jan.1st 2007, Ministry of Finance of People’s Republic of China request all the Chinese listed companies in and out of mainland China must set the new Chinese Accounting Standards as their accounting rules, topics about the impact of new CAS adoption became more and more popular. Because the new CAS is pretty close to the new IFRS, so we predict it will increase the auditing complexity and force the audit fee getting higher. In this paper, we will construct a regression model by consulting Choi et.al., (2010), it could help us easier to measure the differences in audit fee between the old CAS and the new one. Our sample contains all the listed companies in mainland China from 2004 to 2009, which are both 3 years before and after the new CAS adoption year. After testing the data, we have found that mandatory new CAS adoption could lead to an increase in audit fees if the new CAS is credibly implemented.