This study uses content analysis methodology to identity number and type of MAO content， and investigates how MAO content affect auditor behavior. We answer two questions. Firstly， can MAO concent affect audit firm change during the next year? Secondly， can MAO concent during the last year affect current audit fees? Firstly， when MAO content number increases， audit firm is more likely to be replaced during the next year， mainly among clients with qualified or disclaimer audit opinion. With more items in last year’s MAO， current audit firm can require more audit fees. Secondly， I separate the MAO content into three types， accounting issue， regulatory investigation or unsettled legal suits， GC issue. For qualified or disclaimer audit opinionwith accounting issue， audit firm is more likely to be replaced during the next year. For qualified or disclaimer audit opinion with any reason or unqualified audit opinion with explanatorary paragraph， current audit firm can require more audit fees premium. Thirdly， we further investigate how MAO content affect the direction of audit firm change. When there are more MAO items on qualified or disclaimer audit reports， smaller audit firms are more likely to accept them during the next year. When there are accounting issues on unqualified audit opinion with explanatory paragraph， larger audit firms are less likely to accept them. When there are issues of regulatory investigation or unsettled legal suits on qualified or disclaimer audit opinion mention， smaller audit firms are more likely to accept them.