Voluntary principle is an important basis for the implementation of the ongoing rural residential land exit. Encouraging farmers to voluntarily exit from the rural residential land is of great significance for realizing the goal of cultivated land protection and promoting urbanization. This study used 483 samples from a survey of the Wuhan metropolitan area as an example. By investigating the relationship between farmer differentiation and their willingness to exit rural residential land, and the intermediary role of value cognition of rural residential land and generational difference in the relationship between them, this study explored the impact mechanism of farmer differentiation on the willingness to exit rural residential land. The results indicate that: (1) The effect of farmer differentiation on the willingness to exit rural residential land include direct positive effect and indirect positive effect through value cognition of rural residential land. The direct effect accounted for 48.54% of the total effect, and the indirect effect accounted for 51.46% of the total effect. (2) Generational difference had a regulating effect on the intermediary role of value cognition of rural residential land. The intermediary role of the young generation of farmers was more intense. But the intermediary role of the old-generation farmers’ value cognition was weakened and tended to be inconspicuous. Therefore, this article put forward the following suggestions to promote farmers’ willingness to exit rural residential land: improving famers’ non-agricultural employment level; guiding farmers to form a reasonable value cognition of rural residential land; and formulating targeted policies and measures for different generational farmers to promote the rural residential land paid-exit.