Abstract: In order to obtain wideband of Acousto-Optic (AO) deflector, curves of the abaxial angle vs ultrasonic wave frequency under different conditions are systematically studied. By solving the Dixon equation of anisotropic Acousto-Optic diffraction in LN crystal, wide-band operating mode of AO deflector is determined. The design parameters show that the band-wide of AO deflector can be efficiently widened by selecting the appropriate direction of incident light and proper abaxial angle of the ultrasonic waves.