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 compression 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.