Currently, the coordination mechanism between national auditing and national supervision is still inadequate. Based on the analytical paradigm of historical institutionalism, this paper systematically reviews the institutional evolution logic of the supervisory-audit relationship, starting from key nodes and path dependence. The study finds that long-term path dependence has led to an unclear division of responsibilities and powers for supervision and auditing, prominent organizational inertia, and difficulty in spontaneously forming a coordination mechanism. However, when key nodes appear, external institutional shocks prompt structural adjustments in the supervisory system, providing an institutional foundation for supervisory-audit coordination. On the basis of the above discussion, this paper proposes optimization paths, including constructing a coordination mechanism that integrates powers and responsibilities, improving the implementation details of supervisory-audit coordination, building a supervisory-audit coordination information sharing platform, and strengthening the performance evaluation of supervisory and auditing personnel.