In this paper, the effects of over-doping of Nd³⁺, Ho³⁺, Dy³⁺ and Ce³⁺ rare earth ions on the preparation and related properties of TSAG ceramics were investigated, and the results show that over-doping of rare earth ions has a certain effect on the micro-defects and transmittance of TSAG ceramics. The existence of a small number of fine particles which are not in the secondary phase on the grain surface, led to the decrease of the transmittance of the ceramic samples. The Verdet constant of rare earth ion over-doped TSAG ceramics is better than that of pure phase TSAG ceramics at the same test wavelength. In addition, YAG/TSAG-based bilayer composite structural ceramics were explored. The YAG/TSAG and YAG/2.0% Ce∶TSAG bilayer composite structural ceramics were successfully prepared, with sub-micron thickness transition layer formed on the contact surface, and the transmittance of the YAG/TSAG ceramics at 1 064 nm reaches 71.0%. The successful preparation of YAG/TSAG-based composite ceramics broadens the application prospects of TSAG materials in high-power lasers.