This paper proposes the concept and constructs comprehensive indicators of unofficial audit team quality on the basis of the previous research. The influence of unofficial audit team on audit quality was tested from two aspects: team size and team quality. The result shows that the size of unofficial audit team does not have a significant impact on audit quality, which is inconsistent with the “significant negative impact” conclusions of previous studies, while the quality of unofficial audit team can significantly improve audit quality; when the two are included in the same research model, the above conclusion remains unchanged. The impact of unofficial audit team quality on audit quality is more valuable. Furthermore, our research examines the moderating role of factors at different levels of audit environment, object and subject in the relationship between the two. This study expands the relevant research on the impact of auditor team on audit quality, and provides empirical evidence and management inspiration for the internal governance of accounting firms.