A generalized high-order finite-difference time-domain (FDTD) method based on Maxwell's curl equations, in which the spatial difference utilizes the discrete singular convolution (DSC) and the time difference utilizes the symplectic integration propagator (SIP), is proposed to analyze three dimensional electromagnetic scattering problems. The proposed method (which is based on DSC-SIP scheme) has demonstrated high stability and enhanced effectiveness compared with the standard FDTD procedure. In addition, there are significant reductions in CPU time and memory space requirements when large grid meshes is used, so it can be applied to the large size target's three dimensional scattering analysis.