The principle of beam steering technology based on Optical Phased Array(OPA) is introduced. By using Fraunhofer diffraction and Fourier transform, the model of OPA is established. The influence of main parameters of OPA on beam steering efficiency is simulated. It shows that the beam steering efficiency of OPA can be improved by increasing duty ratio, and decreasing total unit size and steering angle; while the number of OPA units has a very small impact on beam steering efficiency.