<p>Quality promotes agriculture and branding strengthens agriculture. The branding of agricultural product is a driving force for agricultural development and an effective choice for realizing farmers’ income, agricultural efficiency and rural development. On the basis of the TAM model and the theory of persuasion knowledge, this paper uses multiple linear regression and stepwise regression to study the influence mechanism of key opinion leader on the brand advocacy of agricultural product from the perspective of key opinion leader. The results show that: key opinion leader’ professionalism, product involvement, and interactivity have a significant positive effect on the promotion of agricultural product brands, while reputation has no significant effect on the promotion of agricultural brand advocacy; key opinion leader’ professionalism, product involvement, interactivity, and reputation significantly promote consumer trust; and consumer trust plays a partial mediating role in the influence of key opinion leader on the brand advocacy of agricultural product. The study integrates a theoretical model for analyzing the impact of key opinion leader on agricultural brand advocacy, and the findings help complement related research on influencer marketing and agricultural brand advocacy. The conclusions of the study provide suggestions for agribusinesses to carry out brand marketing in new media, which can help create a clear and satisfying online consumption environment for consumers.</p>