Abstract: The key ecological function area plays an important role in providing ecosystem service. As the main players of economic activities in this area, the excessive dependence of local farmers on environmental resource will seriously influence ecological environment quality, and thus impair the ecosystem service. At present, it is urgent to explore the dependence of farmers’ livelihoods on environmental resource and its influencing factors in key ecological function areas, which would provide reference for the formulation of environmental friendly regional development policies. We selected the Gannan Plateau as study area. Based on 581 survey data, we analyzed the dependence of farmers’ livelihood on environmental resource, and used the ordinal multi-class Logistic regression model to identify its key impact factors. The results showed that local farmers were highly dependent on environmental resource in Gannan Plateau, which was mainly reflected in three aspects of food self-sufficiency, daily energy consumption and income source, with the dependence of 57.3%, 56.9% and 37.4%, respectively. There were significant differences in the dependence of different types of farmers’ livelihoods on environmental resource, in that farmers with higher levels of education and higher non-agricultural levels had lower dependence and the farmers with high dependency ratio were more dependent on environmental resources. The factors including family dependency ratio, labor education level, proportion of migrant workers in labor force, family member leadership, ecological policy, and altitude had significant impact on farmers’ environmental resource dependence. Among them, family dependency ratio and altitude had positive impact on it, while the proportion of migrant workers in labor force, labor education level, family member leadership, ecological policy had negative impact.