Different from backlight for panel display, the backlight for integral imaging should be directional in order to improve the viewing quality. A method for eliminating the flipped image and improving the optical efficiency for integral imaging is proposed by using directional backlight with diffractive grating. The light from one elemental image reaching the neighboring elemental lens can be eliminated with directional backlight. The effect of the backlight angular divergence and pixel structure on crosstalk and the viewing angle is analyzed. Simulation and experiment show the validity of the proposed method.