Objective To study the effects of living environment conditions and animal-animal interaction on the blood hormone levels and psychological behavior in Chinese tree shrews. Methods Chinese tree shrews were raised in cages of different space sizes or were administered reserpine for 15, 30, 60, 120, 180 days, respectively. Then the animals were anesthetized by ether inhalation, and blood samples were taken from the heart to detect the levels of blood testosterone (T), estradiol (E2), endothelin (ET), adrenaline (A) and noradrenaline (NA) by radioimmunoassay (RIA). Results 1. Chinese tree shrews were bred in large cage (D1group) or small cage (X1 group) for 15, 30, 60, 120, 180 days, respectively. Compared with the animals bred in the large cage (D1 group), the level of blood testosterone (T) was significantly reduced (P< 0.01), and the levels of adrenaline, noradrenaline and endothelin were significantly increased in the small cage group (P< 0.01 for all). 2. The animals raised in small cages in close neighborhood with large cages for 15, 30, 60, 120, 180 days, respectively. The levels of testosterone, adrenaline and noradrenaline in the large cage group (X2 group) were significantly higher than those of the small cage group (X1 group) (P< 0.01 for all). 3. The adrenaline and noradrenaline levels were significantly lower in all the reserpine groups (P<0.01 for all). 4. The animals bred in small cages (X1 group) and in small cages in close neighborhood with large cages showed sudden loss, reduced appetite, testicular atrophy, penile prolapse and stress symptoms. The animals of the reserpine groups appeared gentle temperament, significantly reduced activity and reduced appetite. However, after stopping the reserpine administration and feeding them in large cages, the animals gradually returned to normal behavior. Conclusion Both animals living environment conditions and animal-animal interaction may cause changes of blood hormone levels and psychological behavior in Chinese tree shrews.