The audit market in China is characterized by“Administrative Leading”.Once the government takes the views，large audit firms provide high quality audits as an important factor when formulating measures related to resource allocation in audit market.Consequently，large audit firms may show significantly opportunism behaviors to cater to the government.The study finds that compared to domestic firms，international large audit firms do not show significantly opportunism behaviors to adjust audit quality depending on any special circumstances.However，the domestic firms audit quality has been improved markedly when policy changes and domestic large audit firms have improved their audit quality more significantly than small ones.