In this paper, the beam characteristics of semiconductor lasers are studied and their far-field images which are the Fourier transform of near-field images are analyzed and deduced. The semiconductor laser beam has a bad directivity and its divergence angles in the fast and slow axes have a large difference which can causes the beam spot emitted by the semiconductor laser to be elliptical. This is disadvantage to its transmission in a long distance, so the collimating technology of the laser beam is also studied.