作为公司治理机制设计的核心袁有效的董事会监督能够抑制代理成本。董事会监督的有效性很大程度上取决于其独立性，并且外部利益相关者的治理参与也有着重要影响。以2012—2020年间沪深股市非金融类公司为样本，关注董事会监督与两类代理成本之间的关系，重点考察政府作为公司最重要的外部利益相关者，其治理参与对董事会监督与代理成本间关系的影响。结果发现，随着董事会监督的加强，两类代理成本趋于降低，政府作为外部利益相关者的治理参与，进一步强化了董事会监督的有效性并降低了代理成本。

As the core of corporate governance mechanism design, effective board supervision can curb agency costs. The effectiveness of board supervision largely depends on its independence. The governance participation of external stakeholders also has an important impact. Taking non-financial companies in the Shanghai and Shenzhen stock markets from 2012 to 2020 as a sample, this paper focuses on the relationships between board supervision and two types of agency costs, particularly the impact of government participation, as the most important external stakeholder, on the relationships between board supervision and agency costs. The results show that, with the strengthening of board supervision, the two types of agency costs tend to decrease, and the government's participation as an external stakeholder further strengthens the effectiveness of board supervision and reduces agency costs.