Abstract: A time-domain physical-optics (TDPO) line-integral representation is developed for the backscattered near-fields from a perfectly conducting surface illuminated by a dipole resource. The proposed representation is derived from time-domain physical-optics (TDPO) surface-integral representation by introducing two theorems:surface gradient theorem and surface divergence theorem. The proposed representation is free from singularities for all the source/observer positions in which the dipole antenna is located. The transient backscattered magnetic fields of metal plate and a complex object are computed. The results are in good agreement with those obtained by other methods. Numerical results show that the method can not only ensure the calculation accuracy, but also greatly improve the calculation speed.