With the development of optical communication technology and photonic integrated circuits, non-reciprocal devices have been widely studied and applied as an important part of optical communication systems. Magneto-optical isolators and circulators based on magneto-optical effect are currently the most widely used non-reciprocal devices. In order to integrate non-reciprocal devices into silicon wafers, magneto-optical thin films with comparable performance to bulk magneto-optical materials need to be prepared. In the near-infrared band (1 550 nm), rare earth iron garnet (RIG) represented by yttrium iron garnets (Y3Fe5O12, YIG) has excellent magneto-optical effects and become one of the most promising magneto-optical materials. It is found that doping with rare earth ions can effectively improve the magneto-optical properties of YIG thin films, especially Bi3+ and Ce3+ doped YIG exhibit giant Faraday effect. In this paper, the Faraday effect principle is briefly introduced, three common growth methods of RIG magneto-optical thin films and their research progress in recent years are reviewed, and the application of RIG magneto-optical thin films in optical isolators and circulators are summarized. Finally, the future development trend of magneto-optical films is prospected.