Sandy desertification is one of the most severe ecological and environmental problems worldwide. Desertification reversion, as the reverse process of desertification expansion, has some instability and vulnerability due to disturbances by numerous socio-ecological factors. We call this phenomenon vulnerability of the desertification reversion process, and define it as the possibility and tendency of a reversion trend decline or reversal. Socio-ecological systems theory is a new form of ecological systems research. Based on this theory, we selected the driving-pressure-status-impact-response (DPSIR) framework and a typical reversed desertification area in Yanchi County as the study area. In this area, human activities have obviously interfered with natural processes and the expansion and reversal of desertification contrast sharply. We constructed an evaluation index system to assess the vulnerability of the desertification reversion process. This system includes four levels, five groups, and forty-one concrete indexes, including a moisture index, an ecological governance index, and sandy proportion. Finally, we explore the logical causality between drivers, pressure, status, impact, response, meanwhile discuss the quantitative calculation method of vulnerability. The objective of this study was to scientifically assess the vulnerability of the desertification reversion process, and to provide support and a scientific basis to make decisions, manage, and regulate the desertification problem in the pastoral transitional zone.