As the key component of optical isolators, magneto-optic(MO) materials play an important role especially in high power laser system to ensure one-way light propagation, protect the laser sources and stabilize the laser output. The recent research progress of the MO materials used in near-infrared high power optical isolators was introduced. The key thermal-optic characteristics of MO materials under high power laser conditions and their effects on device performance were illustrated in detail. The studies and high power performance of several newly developed MO material candidates like TSAG crystal, TAG ceramic, and TGG ceramic were reviewed and compared with the commonly used TGG single crystal and Tb-doped glasses on aspects of Verdet constant, thermal conductivity, magneto-optic figure of merit and so on. Among them, TAG ceramics were discussed emphatically including the effects of ions doping and synthesis technology on its magneto-optic and thermal-optic properties. At last, the newest progress on the study of TAG ceramics was introduced, as well as the application prospect and research trend of MO materials used in the 3-5 μm mid-infrared region.