Using the surface impedance boundary condition (SIBC)-finite difference time domain (FDTD) method, the electromagnetic scattering characteristic of non-magnetized plasma coating on metal material is obtained, under the one-dimensional (1D) oblique incident wave condition. The SIBC method can greatly reduce computational memory by ignoring the mesh division of the background material. Firstly, the expression of frequency domain surface impedance is derived, and substituted into boundary condition equation. Then the equation is transformed to time domain via Fourier inverse transformation method, and the formula is quantized to obtain the update equation by piecewise linear recursive convolution (PLRC) method. The algorithm is used to calculate the reflection coefficients of parallel and vertical polarization waves at oblique incident angels. The comparison of the SIBC-FDTD results with analytic solutions shows the validation and effectiveness of proposed method. Finally, the effect of incident angle on reflection coefficient is analyzed by this method.