Abstract: In this paper,ways to design LiNbO₃ anisotropic acousto-optic device based on beam steering theory are studied.The accurate design parameters for plane configuration and step configuration are systematically calculated.The result shows that anisotropic acousto-optic device using LiNbO₃ crystal can realize optimum design with beam steering theory;it can gain wide 3 db bandwidth and high diffractive efficiency simultane- ously.The research also shows that acousto-optic device designed in step configuration gains a higher energy utilization ratio comparing with that of the plane configuration.