We studied population parameters and physiological characteristics in Brandt′s vole (Lasiopodomys brandtii) across periods of breeding and non-breeding near Aershanbaolige Town, Inner Mongolia. Here, we show that the breeding population built more burrows, had a non-biased sex ratio, and was composed of overwintering and newborn voles. During non-breeding periods the population occupied relatively fewer burrows, had a male-biased sex ratio, and was comprised of newborn voles only. Cleaned carcass index was higher in non-breeding populations and in males, and indicated that these animals had better nutritional status. Low adrenal gland and high spleen indices in non-breeding populations revealed lower stress and stronger immunity during that season. Our results suggest that there are significant differences in population parameters and physiological characteristics in Brandt′s vole, which is related to variation in life strategies during breeding and non-breeding seasons.