Abstract: Analyzing the impact of contract farming on farmers’ soil quality conservation behaviors and its underlying mechanisms provides insights for enhancing soil quality. Based on data from 565 farming households across 10 counties in Jiangxi Province, empirical analysis was conducted using ordered Probit models, mediation effect models, and moderation effect models. The findings reveal: (1) Contract farming significantly promotes farmers’ adoption of soil quality protection behaviors and drives them toward adopting a combination of multiple soil quality protection measures; (2) Contract farming indirectly promotes farmers’ soil quality protection behaviors through three pathways: facilitating farmers’ participation in agricultural industry organizations, increasing their involvement in agricultural technical training, and improving the input-output ratio of agricultural operations; (3) The promotional effect of contract farming on farmers’ soil quality protection behaviors exhibits significant scale heterogeneity and high-standard farmland construction heterogeneity. Compared to large-scale farmers and farmers without high-standard farmland construction, contract farming has a more pronounced promotional effect on soil quality protection behaviors among small-scale farmers and farmers with high-standard farmland construction; (4) Internet usage level significantly positively moderates the impact of contract farming on farmland quality conservation behavior. The higher the level of internet utilization for accessing agricultural information, the stronger the guiding effect of contract farming on farmland quality conservation behavior. Based on these findings, embedding contract farming within the farmland quality conservation policy framework and strengthening agricultural industrial organization, agricultural technical service provision, and agricultural digitalization are crucial measures to guide farmers in continuously improving farmland quality.