The Striped Hamster is a major agricultural rodent of the North China Plain,and understanding the mechanisms regulating the fluctuations of its populations is important for maintaining the ecological balance.Fluctuations in Striped Hamster populations occur between years and within seasons,but the mechanisms involved are not well understood.In this study,the Striped Hamsters were collected on 10 occasions in spring and autumn between 2004-2008 from Wu village,Qufu city,Shandong province.The relative densities of the Striped Hamster populations were estimated by the rate of trap success.The genetic structure of the 10 Striped Hamster populations was determined using microsatellite markers.The results show that annual and seasonal fluctuations exist in the genetic structure and the population density,and a positive correlation exists between the genetic diversity and the population density; the genetic diversity of the spring populations is significantly higher than that of the autumn populations,while the population density of the spring population is significantly lower than that of the autumn populations.These results suggest that the genetic diversity of the Striped Hamster population is density and season dependent; density and season may be main factors affecting the genetic structure of the Striped Hamster populations.