The “giant” beaver, Trogontherium cuvieri Fischer, 1809, is an extinct species that was widely distributed from the Late Pliocene to the Late Pleistocene all over the Palaearctic Realm. The global environment during this period is characterized by periodic and extreme climate changes, and most mammalian groups experienced rapid evolution during this period. However, the morphology of T. cuvieri shows long-term stability or conservatism, so theoretically it must have adopted certain ecological strategies to cope with drastic changes of climate. New T. cuvieri materials from Jinyuan Cave cover 5 different horizons from Early Pleistocene to Middle Pleistocene (from ~2.1 Ma to ~0.5 Ma by magnetic dating). Its five occurrences are not coupled with climate change in Northeast China. To explore how its persistence in this area in the Pleistocene could help us understand the ecological adaptation mechanism of the species, we used tooth micro-wear analysis to establish a micro-wear feature matrix for T. cuvieri from different horizons, and performed a statistical analysis based on this matrix. The results of ranking analysis show that there are significant differences in the diet of T. cuvieri in different chronological periods, which demonstrates that a plastic ecological niche is an important mechanism for the species’ ecological adaptation, and is possibly the principal factor in persistence of T. cuvieri in Northeast China.