Group sizes of Brandt’s vole ( Lasiopodomys brandtii )overwintering colonies could affect colonies’ predation risks. We studied how the different group sizes of Brandt’s vole affect the predation preference in Xilinguole typical steppe, Inner Mongolia, Abagaqi Centre from September 25 to October 15, 2014. Meanwhile, we tested the effect of the predation preference of the steppe polecat (Mustela eversmanni) on the group size of the Brandt’s vole within the sampling area. Recapture method and MNA method were used to estimate the Brandt’s family quantity. Meanwhile, both the amount of feces of the steppe polecat and holes dig by the steppe polecat within the ground of each Brandt’s vole colony was recorded as the indicator of its predation preference. 91 colonies of Brandt’s voles and 658 Brandt’s were observed within the sampling area, among them 17 Brandt's vole has new feces, 5 Brandt's vole were dug by the steppe polecat (the sampling area is 4hm2) . Then the Mann-Whitney U of nonparametric was used to analyze the data. The results show that the rank sum of the colonies where no feces of the polecat were recorded is 1096, while that of the colonies with feces records is 3090 (U value = 315, Adjusted Z Value = ?3.241, Adjusted P Value = 0.0012); At the same time, the rank sum of the colonies whose holes were dug by the polecat is 429, comparing with the colonies no dig , the rank sum is 3757 (U value = 16, Adjusted Z Value = ?3.514, Adjusted P Value = 0.0004).This suggests that the difference between the two groups of colonies is significant. This difference indicates that the steppe polecat significantly prefers to high number of group sizes of Brandt's vole colonies, they tend to spend longer time around the colonies with more holes, some of them even tried to dig those colonies to hunt, therefore, more feces and excavation trails can be found around the ground of those colonies .This finding indicates that the colonies with larger size result into a higher predator risk.