<p>Governance evaluation represents a fundamental issue and a critical link in assessing the effectiveness of government governance. It is widely acknowledged that social trust serves as a pivotal factor for effective governance. However, existing research primarily concentrates on the correlation between social trust and objective measures of governance performance, lacking a systematic exploration of how social trust influences governance evaluation and the underlying mechanisms involved. Based on the relevant data from the “2021 China Social Survey (CSS2021),” a quantitative study was conducted on the relationship between three types of social trust of Chinese farmers and their evaluation of grassroots government governance. At the same time, the mediating effect of fairness perception and its sub-dimensions among was explored. The study findings demonstrate that social trust has a positive impact on the evaluation of grassroots government governance in rural China. Specifically, trust in government exerts the most significant influence, highlighting the predominant role of grassroots governments in rural governance in China. Furthermore, fairness perception and its sub-dimensions serve as causal mediators between social trust and the evaluation of governance at the grassroots level, validating the importance of social equity as a primary objective in rural governance. This research unpacks the complex relationship between social trust and the evaluation of grassroots government governance, elucidates the differentiated pathways, and establishes fairness perception and its sub-dimensions as key transmission mechanisms. It provides significant reference for optimizing grassroots government governance strategies and enhancing rural governance effectiveness.</p>