Abstract: The paper reviews the study on evolution of endothermy in animal,including the concepts,characteristics and the selective factors.There are eight main hypotheses about the selective factors on evolution of endothermy in animals,including Thermal Niche Expansion Model,Homeothermy and Metabolic Efficiency Model,Decreasing Body Size Model,Postural Change Model,Increasing Brain Size Model,Aerobic Capacity Model,Parental Care Model and Assimilation Capacity Model.The last three are the most important hypotheses.The Aerobic Capacity Model suggests that selection acted mainly to increase maximal aerobic capacity that supports physical activity,and elevated resting metabolic rate evolved as a correlated response.Intraspecific studies on vertebrates support that maximal metabolic rate is correlated to resting metabolic rate,but the interspecific data only give limited support.The Parental Care Model hypothesizes that endothermy is arisen as a consequence of selection for parental care because endothermy enables a parent to control incubation temperature.The Assimilation Capacity Model suggests that the endothermy evolution in birds and mammals is driven by two factors:1) a selection for intense post-hatching parent behavior,particularly feeding offspring,and 2) the high cost of maintaining the increased capacity of the visceral organs necessary to support high rates of total daily energy expenditures.