Abstract: The magnetic field integral equation is analyzed in vector way after it is discreted in frequency domain. It can be found that the arithmetic operator which includes frequency element in the matrix equation only contains the vector information of the scattering body's shape. So we can draw a conclusion that the distribution of poles is only due to the exterior shape of the scattering body. We also studied this problem with FDTD method, calculated the cone's poles from the scattering data in late time in different scattering directions, and found that the position of poles are all agreed with the theoretical results well. It is proved that the distribution of poles can not be affected by the change of target pose.