The present disclosure provides a field of display technologies, and in particular, to a LTPS substrate and a fabricating method thereof, a thin film transistor thereof, an array substrate thereof, and a display device thereof. The LTPS substrate, able to be used for the fabrication of a thin film transistor, includes a light shielding layer, the light shielding layer mainly composed of amorphous silicon doped with a lanthanide element. The present disclosure mainly employs an amorphous silicon film layer doped with the lanthanide element as the light shielding layer of the LTPS substrate, which not only ensures the light shielding efficiency but also reduces the production process, and further prevents the occurrence of the H explosion problem due to H exuding during the ELA process.