The uniaxial compression tests with equal strain rate were carried out using the UTM 25 multifunctional material test system and specially designed radial strain test device. The relationships between the stress（axial direction）, strain（axial, radial and volumetric strain） and loading time were analyzed at 30, 40, 50, 60℃ for further studying the shear dilative mechanism of asphalt mixture. According to test results, the shear dilative behavior of asphalt mixture is temperature dependent. On the process of volumetric strain change with loading time, the asphalt mixture in beginning period of applying load shows shear shrinkage, but with loading time it soon exhibits shear dilation under the softening point of asphalt binder. There is no shear shrinkage when the whole process is done upon the softening point of asphalt binder. The dilative behavior of asphalt mixture is caused by the anisotropy property of asphalt mixture, the looseness of interlocks between particle elements in asphalt mixture and the lubrication provided by asphalt for mixture, especially when the temperature is higher than softening point of asphalt binder.