本文提出了一种计算数值绕射系数的有效方法，并将之用于提取表面具有分形结构金属劈的绕射系数。利用时域有限差分（ＦＤＴＤ）法提供的散射场，根据几何绕射理论（ＧＴＤ）建立含有绕射系数未知量的方程组，通过联立方程组的求解，得到散射体边缘的数值绕射系数。具体计算例子表明，该算法是有效的。 In this paper, an effective method to calculate the numerical diffraction coefficient is proposed and used to extract the diffraction coefficient of the metal wedge with the fractal structure on the surface. Based on the theory of geometrical diffraction (GTD), a system of equations containing diffraction unknowns is established by using the scattering field provided by the finite-difference time-domain (FDTD) method. By solving the simultaneous equations, the numerical diffraction coefficient . The concrete calculation example shows that the algorithm is effective.