Orbital angular momentum (OAM) carried by the vortex beam provides a new dimension resource in the spatial domain of light waves, which attracting more and more researching attentions. Since the vortex beams with different OAM mode values are orthogonal to each other, the OAM mode is introduced into the field of traditional optical communication, and two new application mechanisms are derived: OAM shift keying (OAM-SK) and OAM division multiplexing (OAM-DM), which provides a potential solution for future high-speed, high-capacity and high-spectrum efficiency optical communication technologies. Based on the basic concepts and theories of OAM beam types and their generation methods, this paper will give a brief overview of typical research cases related to the application mechanisms of these two communication systems. Three key technologies have been discussed, including OAM beam multiplexing technology, OAM beam demodulation technology, and turbulence suppression technology of OAM-based optical communication. Finally, the future developing trends and prospects of OAM-based optical communication technology are analyzed and forecasted.