Abstract: Mongolian gerbils had high ability to endure both high and cold temperatures. To study the mechanism of high ability for thermal adaptation, gerbils were acclimated to high temperature (30 ℃) for 8 weeks, and were measured for metabolic features, body composition as well as mitochondrial content and activities. Lipidomic techniques were used to measure changes in mitochondrial membrane, including potential mitochondrial membrane remodeling during acute thermoregulation in gerbils. Heat acclimated gerbils showed lower basal metabolic rates but no changes in adaptive non-shivering thermogenesis were detected. A significant mitochondrial membrane remodeling with increases in monounsaturated/polyunsaturated free fatty acids ratios was associated with the decrease in metabolic rate. During heat acclimation, mitochondrial cytochrome C oxidase activity was elevated in brown adipose tissue, presumably caused by the increase in membrane unsaturation. Our results indicated that mitochondrial membrane remodeling is an important mechanism during heat acclimation in Mongolian gerbils, to reduce the metabolic rate in general while preserving sufficient capability to respond to acute cold. Such a mechanism may allow gerbils to cooperate with wide range of daily and seasonal temperature fluctuations.