Relocation is an important way to win the fight against poverty. It is of great significance to explore the livelihood adaptability of rural migrants to consolidate the results of the fight against poverty. Based on the framework of sustainable livelihood approach and a field survey data of Fenghuang County, Hunan Province, this paper analyzed the impacts of human capital on rural migrants’ livelihood adaptability and explored the mechanism of human capital on migrants’ livelihood adaptability by the multiple regression model, the mediating effect model, and the moderating effect model. Results show that the health status of rural migrants in Fenghuang County is good, but they are less educated, and some families are with heavy burden. The overall human capital of migrants is weak. From the perspective of livelihood adaptation, the degree of social adaptation of migrants is high, the degree of psychological adaptation is low and the adaptability of livelihood is weak. Human capital significantly and positively affects the livelihood adaptability of migrants and credit support plays an intermediary role partly in the process of human capital improving livelihood adaptability. The diversity of livelihood strategies play a positive moderating role in the relationship of human capital improving credit support. Therefore, in order to ensure the achievement of relocation, this paper suggests: continuously enhancing the livelihood adaptability of rural migrants, improving the governance mechanism of the resettlement area, speeding up efforts to strengthen areas of weakness in medical care and education, promoting the development of facilities to ensure employment, and increasing financial support.