Suppliers are important members of the agricultural product supply chain, and their behavior decisions may have a certain impact on the sustainable development of the agricultural product supply chain. From the perspective of agricultural product supplier trust, this paper studies the direct impact of agricultural product supplier trust on relationship quality and the indirect impact of supplier fairness perception on relationship quality. Based on the survey data of agricultural product suppliers, this paper uses the structural equation model method for empirical analysis. The analysis results show that fairness perception and trust perception have a significant positive impact on the quality of agricultural supply chain relationships, among which trust perception has a positive direct impact on the quality of agricultural supply chain relationships, while fairness perception has indirect influence on the quality of agricultural supply chain relationships through trust. In addition, information sharing, price satisfaction, income level and environmental certainty have a significant positive impact on suppliers’ fairness perception. Therefore, sellers comprehensively consider the fairness perception and trust perception of suppliers, which will help improve the relationship quality of the supply chain.