Farmland protection is the most important land science research issue in developing countries, especially in China, due to serious land degradation. This paper aimed to reveal the causal chain among driving factors, farmers' land protection perceptions, behavioral responses, and land quality change by applying a structural equation model (SEM), based on a cross-sectional dataset of 238 households surveyed, and matched plot soil sample results in the Sujiatun District, in Liaoning province, China. The results show that, compared to internal factors, external factors play more important roles in shaping farmers' land protection awareness which subsequently transfer into land protection behaviors. Various land use behaviors lead to different impacts on land quality, in which the crop planting structure and land input density have dominant effects on changes in the soil nutrient content. The results imply that a stable and reasonable price mechanism for agricultural inputs and outputs is meaningful to land protection. Moderate land circulation would help reduce land fragmentation, develop agricultural modernization, improve production efficiency, and achieve economies of scale. In addition, knowledge, training and environmental policy information on farmland protection play key roles in land conservation activities. These main results have important implications for policymakers with regard to promoting land protection activities, alleviating land resource and environmental pressures, and thus achieving the goal of sustainable land use.Sustainability 2018, 10, 3345 2 of 17 will probably adopt some land conservation practices, in terms of using organic fertilizer and formula fertilizer, and these behaviors may further change their perspectives. Therefore, there are important theoretical and practical reasons for investigating the interrelations among farmers' land protection perceptions, behaviors and farmland quality changes from a microcosmic perspective.Some studies have focused on farmers' willingness to protect their farmland, and the influencing factors [19,20]. The characteristics of farm households and farmlands, as well as land protection policies, are closely related to farmers' perceptions of land protection [7,21,22]. Farmers' age and education positively affect land protection awareness, indicating that older farmers with higher levels of education are more likely to form stronger land protection intentions [23]. A dependence on agricultural income plays a promoting role in farmers' willingness towards land protection [24,25]. A sense of moral responsibility also has a positive effect on land protection cognition. Specifically, farmers are more willing to implement farmland conservation, due to a stronger sense of moral responsibility, implying that land protection policy should be focused on motivating farmers' sense of social responsibility [26]. However, land fragmentation seriously weakens farmers' enthusiasm to protect their farmland [27].According to the theory of planned behavior and relevant empir...