Abstract: In this paper,basic theory about optimum design by using ultrasonic steering technology in isotropic acousto-optic deflector(AOD)is introduced.Curves of relative bandwidth vs acousto-optic interaction relative length in ultrasonic steering AOD and ultrasonic non-steering AOD are given respectively.Through analyzing these curves,it can be obtained that the ultrasonic steering AOD can overcome contradiction between big bandwidth and condition of into Bragg diffraction region or between big bandwidth and big diffraction efficiency in the non-steering AOD.When the acousto-optic interaction relative length of the two devices are equal,the relative bandwidth of the steering AOD will be 5.2 times as great as the non-steering AOD.When the relative bandwidth of the two devices are equal,the acousto-optic interaction relative length of the steering AOD will be 4.8 times as great as the non-steering AOD.