Auditor industry specialization means strong professional competence in specific fields, which has a significant impact on preventing audit risks and improving audit quality. Focusing on the theme of auditor industry specialization affecting the threshold of financial audit materiality, and combining the moderating effect of the nature of equity, 2016—2018 A-share listed companies were selected as research objects for empirical testing. The results show that auditor industry specialization has a positive impact on the threshold of materiality. If the audited unit is a state-controlled listed company, then the positive correlation between auditor industry specialization and the materiality threshold is more significant. The results are of reference value to the allocation of human resources of audit institutions and the improvement of relevant systems and supervision by supervisory departments.