In the region of slab-rent structure rock mass，the representative rock blocks(i.e.，slab rupture protolith)，in which the slab rupture has occurred，were selected. To obtain the anisotropic properties for related strength parameters，the uniaxial compression tests with the loading direction vertical and parallel to slab rupture direction are performed. At the same time，the analysis of mesoscopic morphology of rupture surface is conducted using scanning electron microscope(SEM). In order to provide the theoretical basis for the rock mass slab rupture，we try to explore the potential inherent connection among the rock mass slab rupture，rock mechanical properties and its composition. The study shows that：the protolith with slab rupture has anisotropic characteristics and close relation with the direction of slab rupture；under the same magnitude of load，the load parallel to the direction of slab rupture is more likely to cause deformation and failure of potential slab-rent rock mass than the load vertical to the slab rupture direction；when the load is vertical to the direction of slab rupture，the rupture surface often shows both transgranular and intergranular fratures but the latter one dominates；when the load is parallel to the direction of slab rupture，the rupture surface is relative smooth and the area with intergranular fracture is larger than the area with transgranular fracture；the defects and damage in the slab rupture protolith are nearly parallel to the direction of slab rupture，and they are not only the foundation of slab rupture，but also be further developed due to the occurrence of slab rupture.