The graphics processor unit-based finite-difference time domain (FDTD) algorithm is applied to study the electromagnetic (EM) scattering from one-dimensional (1-D) large scale rough soil surface at a low grazing incident angle. The FDTD lattices are truncated by a uniaxial perfectly matched layer, and finite difference equations are employed in the whole computation domain for convenient parallelization. Using Compute Unified Device Architecture technology, we achieve significant speedup factors. Also, shared memory and asynchronous transfer are used to further improve the speedup factors. Our method is validated by comparing the numerical results with those obtained by using a CPU. The influences of the incident angle, correlation length , and root-mean-square height on the bistatic scattering coefficient of a 1-D large scale rough surface at low grazing incidence are also discussed.