The administrator boundaries in room were modeled by digital filters of complex impedance in finite-difference time-domain (FDTD) method. Doors, windows and walls were described respectively by their complex impedance boundaries with digital filters. Impulse responses in a room were calculated with the FDTD model, and typical room acoustics parameters were obtained from the responses. The high correlation coefficients between the calculated and measured impulse responses and the good agreement in acoustic parameters show that sound field in room can be properly simulated by this FDTD model.