Microphone arrays are widely used in the applications for acoustic source localization. The interest in signal processing techniques for deriving directional information from small-sized arrays of microphones in far field model is steadily growing. And beam forming is a robust method for source localization, which aims at estimating the source position by maximizing the response output by the microphone arrays in the source direction. In this paper, we focus on the sound source orientation in far field modal. In order to estimate the probability of the sound source point in the plane that we have assumed, the plane is divided into grids with the same size and then we use autocorrelation method to evaluate the possibility degree of each grid and after being normalized we use Matlab to show the distribution of the possibility to orient the actual position. And in the experiment, the moving noise sound, which gives out continuous sound and keeps changing the position, is used to detect the accuracy of the algorithm. Furthermore, the use of interpolation method and autocorrelation matrix in beamforming estimation can overcome the orientation error caused by the data limit and compute at a corresponding fast speed.