The study looked at how good corporate governance and ownership structure affect the relationship between agency costs and firm performance in Chinese companies. They found that better corporate governance, higher ownership concentration, and non-state ownership can improve firm performance by reducing agency costs. On the other hand, state ownership can have a negative impact on firm performance. This suggests that investors should consider agency costs when choosing stocks, and that state-owned firms may have higher risks of managerial abuse. Policymakers can use these findings to create rules that protect investors and minimize managerial abuse in companies.