ABC(Absorbing Boundary Conditions) is an important component part in FDTD(Finite-Difference Time-Domain) method,the processing of corner point affect ABC itself,that is,the inadequate processing of them may cause unnaturally results.The processing of corner points in traditional second-order absorbing boundary condition for 2D case is complex,and it is difficult to extend to 3D case.For these reasons,a simpler method about the corner points based on unidirectional out traveling wave absorbing theorem is discussed in this paper,and validated by a numerical method proposed by authors.The results show that this method satisfies the demands for ABC and is more efficient and more precise.Meanwhile,it is easy to extent to 3D case.