从基本的差分概念和Maxwell方程出发,引入电磁场方程的Hamilton函数.提出一种基于Runge-Kutta-Nystrom辛算法的高阶时域有限差分方法,该方法保持了系统的相空间体积不变和总能量不变,并导出了迭代公式.在此基础上计算了一种金属圆柱的雷达散射截面.计算结果表明该方法的正确性及快速、精确的特性. Based on the basic concept of difference and Maxwell’s equation, the Hamiltonian function of electromagnetic field equation is introduced. A high-order finite difference method based on Runge-Kutta-Nystrom symplectic algorithm is proposed. This method keeps the volume of the phase space constant and the total The energy is not changed, and the iterative formula is deduced. Based on this, a radar cross section of a metal cylinder is calculated. The calculation results show that the method is correct and fast and accurate.