Food selection by animals is determined by their food resources, food quality and food preferences. Although livestock grazing can significantly decrease quality and quantity of the preferred-plant by rodents, it is still not clear how rodents respond to livestock grazing in their food selection. During May to October 2014, we conducted a food selection experiment in the Maodeng pasture, Xilinhot of Xilingol League in Inner-Mongolia. Based on vegetation changes in large-scale enclosures after five years livestock grazing experiment, we investigated food selection of the Brandt’s voles by using cage experiments. We found that grazing increased the coverage of Cleistogenes squarrosa, and decreased the coverage of Leymus chinensis and Stipa krylovii. Cleistogenes squarrosa was the predominant plant species in the enclosures. Grazing had no significant influence on the absolute feeding frequency on three plants by Brandt’s voles. There was no significant difference in feeding frequencies of Stipa krylovii and Cleistogenes squarrosa between seasons, but the feeding frequency of Leymus chinensis was highest in summer. The preference ranking of the three plants by voles was: Leymus chinensis > Stipa krylovii > Cleistogenes squarrosa. However, both seasonal and grazing factors showed no significant impacts on preference index of the three plants by voles. Our results indicate that food selection by Brandt’s voles was relatively stable under grazing pressure, suggesting they had high capacity for adapting to the changing food resources caused by grazing and seasonal factors. We speculate that Brandt’s voles achieve the balance of food components by adjusting feeding efforts.