Abstract: Based on the genetic types of depositional structure planes,the deformation and failure characters are analyzed and their mechanical characteristics and mechanical effects are studied through theoretical analysis and experimental investigation.It is shown that the weak plane of sedimentary structure such as the bedding of weak plane type,sets or cosets plane,bedded plane and unconformity interface will produce main influence on the mechanical properties of sedimentary rock mass.The differences of rock mass’s mechanical properties in parallel and vertical directions of bedding plane are analyzed too.It is displayed that the compressional wave velocity and elastic modulus are lower in vertical directions compared with that of parallel,correspondingly the tensile strength is smaller while the compressive strength and cohesion are contrary.The sedimentary rock mass is prone to produce tensile failure in vertical directions of structure planes and shear failure in parallel directions.Therefore,the rock mass of coal roof tends to generate the destruction phenomenon of separation layer in the direction of stratification plane under the effect of mining.Further,the deformation and failure mechanism is revealed.