Population fluctuations can have a pronounced effect on genetic diversity, behavioral adaptations, and population viability in small mammals. Little is known as to how genetic diversity is associated with population dynamics, and whether genetic bottlenecks or genetic resilience occur in fluctuating populations of small rodents. Using DNA microsatellites and 6 years of data, we investigated changes in genetic diversity of the greater long-tailed hamster (Tscherskia triton) at 2 sites in the North China Plain. Genetic diversity was measured as mean number of alleles per locus (N_a), allelic richness (A), expected heterozygosity (H_E), and observed heterozygosity (H_O). Genetic diversity changed rapidly with changes in population density, and the relationship was positive. A bottleneck effect was detected only in some low-density years. Our results demonstrate an obvious genetic resilience and capacity for recovery in this species. We discuss this pattern in the context of dispersal and other behaviors of greater long-tailed hamsters, and how agriculture-related disturbance affects their genetic diversity.