Experiments are carried out to study the influences of temperature and confining pressure on natural gypsum rock strength and deformation properties under triaxial compression using servo-controlling testing machine. The results indicate that gypsum rock has obvious plastic flow property under different confining pressures. There is no obvious shear failure surface but lateral dilation is observed. Based on Coulomb-Mohr theory

the strength criterion and shear strength parameters of gypsum rock are obtained. With the increase of temperature

the strength of gypsum decreases. At high temperature

gypsum dehydration process takes place with result of transformation from gypsum to bassanite. Scanning electron microscope (SEM) and X-ray diffraction (XRD) methods are used to study the process. With the dehydration process

the pore pressure increases and the failure property becomes brittle. With load continuing

failure surface tends to heal. Obvious plastic flow characteristic and fast self-healing property of gypsum rock are fundamental to sealing stability of natural gas caprock.