This study examines whether nonaudit service and auditor tenure affect audit quality and explores further whether auditor tenure affects the relationship between nonaudit service and auditor dependence. Using discretionary accruals as the proxy for audit quality, we find that nonaudit service has a significantly positive association with the absolute-value and positive discretionary accruals. This result suggests that material nonaudit service may impair auditor independence. Besides, we find that the absolute-value and positive discretionary accruals significantly decrease as audit tenure extends, and longer auditor tenure mitigates the adverse effects of nonaudit service on audit quality. Therefore, the results suggest that longer auditor tenure does not have adverse effects on audit quality; instead, it constrains the earnings management through discretionary accruals.