Effects of the audit tenure on the audit quality in China were studied by investigating the effect of auditfirm and audit-partner tenure on two proxies of audit quality: (1) auditor's propensity to issue a going-concern audit opinion for distressed companies, and (2) the direction and amount of abnormal working capital accruals.  For the former as the proxy variable, there is no linear relation between the tenure and audit quality.  However, when we turn to use the latter as the proxy variable, we find that longer tenure helps to produce higher audit quality.  Moreover, we find evidence that there exists knowledge spillover effect within audit firms when the clients have incentive to increase their earnings.  A further analysis shows that the main previous finding on abnormal accruals is attributable to the non-Big 4 auditors, which implies that the positive effect of auditor tenure's knowledge and expertise is more important for non-big 4 auditors.