Abstract: The survival strategy of animals in environment stress is one of ecology hot projects for scholars to study nowadays, the problem that biochemical physiology responses of animals to hypoxia environment is focused by scholars for long-term. As a famous model, the freshwater red-eared turtle, Trachemys scripts elegans, is one of the hypox-ia-tolerant animals for studying in biology and medicine field, especially at lower temperature, and it has more ex-cellent mechanisms to adapt hypoxia stress. Effects of acute hypoxia stress on carbohydrate metabolism and antioxidant defense of red-eared turtle was studied at 20℃, and the adaptation of the turtle to acute hypoxia stress was discussed in this paper. Within the thermostat at 20℃, the red-eared turtles were randomly divided into four test groups (at 3, 6, 12 and 24h respectively of hypoxia in the containers with oxygen-poor water) and one control group (at 0h). We took out five turtles respectively on time, the blood was collected from its heart, then the liver, cardiac muscle and skeletal muscle were cut, and tissue homogenate solution was prepared as normal method. The lactate consistency, glycogen content, plasma glucose level, Na+-K+-ATPase activity, superoxide dismutase (SOD) activity, catalase (CAT) activity and malonaldehyde (MDA) content of different tissues were assayed by using biochemical methods. After hypoxia-treatment, the phenomenon showed that the turtle's struggle aggravated gradually in early hypoxia, but the struggle weakened gradually in later hypoxia. After 27h hypoxia-treatment, the turtles died successively. The turtle's heart rate of each test group was markedly slower than that of control group, and the longer the hypoxia-time was, the slower of heart rate was. Results of biochemistry indexes indicated that as the hypoxia time prolonged, compared respectively with control group, liver glycogen (reduced by 23%, 36%, 57% and 74%) and muscle glycogen (reduced by 19%, 31%, 43% and 58%) were depleted gradually, liver lactate (increased by 1.3, 2.4, 2.8 and 3.1 fold), muscle lactate (increased by 1, 1.5, 1.8 and 2.2 fold) and cardiac lactate (increased by 1.3, 1.5, 1.6 and 1.9 fold) were rose gradually, while plasma lactate (increased by 9.4, 15.2, 19.1 and 18.4 fold) and glucose (increased by 4.4, 4.7, 5.5 and 6.2 fold) rose rapidly, and the Na+-K+-ATPase activities of cardiac muscle and skeletal muscle felled (*P0.05); the SOD and CAT activities of various tissues increased (*P0.05) and then decreased, and MDA content changed accordingly too. Results suggested that the carbohydrates were resolved rapidly by anaerobic respiration for red-eared turtle in acute hypoxia environment at 20℃. The liver glycogen was used as the main fuel source for anaerobic metabolism, and it resulted in increase largely of plasma lactate and glucose. Hypoxia stress resulted in fall of Na+-K+-ATPase activity. The turtle's antioxidant defense started in time, but its ability to clear away oxy-radical is limited. It followed that a series of stress chain responses to hypoxia stress might happen, such as glycogen broken down?- glucose rising - lactate rising - ATPase activity falling - ATP output decreasing' and oxy-radical increasing - lipid peroxidate increasing - antioxidase activity rising'.