Disaster induced by softening of saturated red-bed soft rocks is one of the major problems encountered frequently in the engineering construction in South China area. Three tests were conducted using the self-developed TAW-100 meso-mechanical triaxial test system of soft rock, including a disintegration test of soft rock in water, a creep test of soft rock under hydro-mechanical coupling condition and a triaxial test by observing the whole deformation and failure process of cracked soft rock under hydro-mechanical coupling condition. The mechanical failure behaviors of saturated soft rock in different engineering environments were investigated to analyze the influences of water, loading, cracks and their coupling effect on mechanical properties of soft rock. Results showed that the process of disintegration and failure of soft rock includes the stages of new crack initiation, slow development, accelerating expansion to penetration and failure. The characteristics of creeping stages of soft rock were consistent during the whole creep process. The coupling effect of water, stress and cracks will accelerate the deformation and damage of soft rock and influence the local mechanical characteristics, the duration of each stage and the final failure mode. The energy transformation and energy dissipation of seepage, chemical and damage in the whole process of soft rock softening under waterstressfracture interaction are analyzed based on the energy theory.