As the core element of corporate governance， the independent director’s background characteristics and embedded network relationship affect their performance of responsibilities and effects of supervision， which in turn influences the audit quality. Based on that， this paper selects listed companies from 2005 to 2015 in Shenzhen and Shanghai stock market as research samples， discussing the influence of independent directors’ background characteristics on the audit quality. The results show that: the independent directors’ tenure and audit quality is inverted “U” type relationship. At the beginning， the marginal effect of independent directors’ independence has an increasing trend， and the independent directors’ strong supervision improves the audit quality； With the extension of the independent directors’ tenure and the strong familiarity of the company’s insiders， the audit quality will decline instead. Independent directors with political connections are difficult to maintain a higher independence， resulting in low transparency of information disclosure and a decline in the quality of audit. The higher degree of education， the more part-time companies，the overseas study or working experience and the background experience of their ?Industry Association are beneficial for the high independence of independent directors and widen the access to information， strengthen the supervision of corporate governance， enhance the transparency of information， and improve the audit quality.