Daurian pika (Ochotona dauurica) is one of the main rodent species in the grasslands of Inner Mongolia, which distributed under grasslands and elm sparse forests, and will form different numbers of overwintering clusters in winter. Steppe polecat (Mustela eversmanni) is one of the main predators of Group size of overwintering colonies of Daurian Pika (Ochotona dauurica) may affect predation risk by mammals. Daurian Pika is one of the main rodent species in the grasslands of Inner Mongolia, which distributed under grasslands and Elm (Ulmus pumila) sparse forests, and will form different numbers of overwintering colonies in winter. Steppe Polecat (Mustela evermanni) is one of the main predators of Dauurian Pika and often attacks the Daurian Pika’s burrow in autumn and winter. To investigate whether the size of the Dauurian Pika’s colony is affected by the risk of predation from Steppe Polecat. We conducted related experiments in the Baiyinxile pasture, Xilinhot City, Xilinguole League, Inner Mongolia, from October to November, 2004. The number of Daurian Pika burrows was used to estimate group size of pika. The number fecal droppings and holes excavated by Steppe Polecat within the habitat of each Daurian Pika colony were recorded as indicators of predation pressure. The nonparametric Mann-Whitney U test was used to detect differences in social group size between the colonies with and without signs of Polecat activity. The result showed that the rank sum of the colonies not surrounded by Polecat feces was 2 700.5, whereas colonies surrounded by Polecat feces was 1 040.5 (U = 422.5, Adjusted Z Value =﹣2.247, Adjusted P < 0.05). The rank sum of colonies with holes dug by Polecat was 461, whereas the rank sum of colonies without the Polecat excavation was 3 280 (U = 120, Adjusted Z Value =﹣2.493, Adjusted P < 0.05) (Table 1). The result of Mann-Whitney test suggested significant differences in predator preference between the two groups of colonies. In addition, the frequencies of feces and excavation trails rise with the increase of group size (Fig. 1 and 2). This difference indicated that the Steppe Polecat significantly preference Daurian Pika colonies with high group size. From the results of this experiment, the existence of the selective predation risk of the Steppe Polecat inhibited the increase of the overwintering clusters of the Dauurian Pikas during the wintering period, thereby maintaining the number of overwintering colonies at a limited scale and level.