Abstract: New test equipment for soils was developed by combining unsaturated triaxial apparatus with electric thermostat-box. It consists of several parts, its volume is small and its weight is light. The apparatus can withstand high temperature and high pressure. Test temperature, suction, stress and strain can be ether controlled perfectly or measured correctly. The precision of measuring total volume change and drainage water volume as well as pore air pressure is satisfactory, and the hysteresis time for transmitting pressure is minor. Test data are gathered and treated automatically by computers. The cost for developing the apparatus was not much. This equipment can be used to perform the test with temperature-controlled for saturated soil or unsaturated soil. Three groups of triaxial tests with temperature controlled for unsaturated expansive soils were carried out, and the test results show that temperature exerts great effect on the mechanical behavior of the soil, such as strain, strength and soil-water characteristics curve et al.