This paper proposes an analysis algorithm that can appropriately distinguish shear failure from bending failure of an RC beam under impact load, by using the SPH method. As structural members, beams generally fail by one of two modes: bending failure caused by excessive bending deformation of the member, and shear failure caused by shear crack growth, leading to rapid destruction at an angle in the web. In this study, to calculate the failure behavior accurately in the local stress field in which shear stress prevails such as when a shear crack occurs, an orthotropic constitutive equation is used. This equation is derived by applying the integrity tensor proposed by Ignacio Carol, Egidio Rizzi and Kasper William, to the usual SPH method. This operation is also extended to the tensile softening characteristic of concrete material. The results confirm that the failure behavior of RC beams under a wide range of conditions can be analyzed accurately by using the proposed algorithm.