Concrete is a sort of inhomogeneous and discontinuous diverse mixture, it has very complicated interior structure and working mechanism[1,2]. But the research about concrete constitutive relation and strength theory was based on the condition of concrete continuity. The law for microcosmic deform during concrete destroy was little considered. Mechanism of shearing failure was researched through concrete sample’s experiment to explored interior microcosmic disharmony and the law of limiting strength release in this paper. Shearing experiments of concrete show shearing displacements of various local district in shearing surface during shearing have apparent discrepancy from beginning to end. This discrepancy leads to destroy of shearing surface from one local to another local and brings course of shearing limiting strength release discontinuous, one-off and non-instantaneous.