Two new dinuclear lanthanide complexes [Ln2(Hsal)3(NO3)6]·(C2H5N)3·nH2O (Ln = Gd, Eu) were synthesized with an aromatic carboxylic acid ligand (salicylate). Both complexes were extensively characterized by various techniques, including elemental analysis, infrared spectroscopy, powder X-ray diffraction, and X-ray single-crystal diffraction. The thermal behavior and photoluminescence properties of lanthanide complexes were investigated. It was found that the two complexes had good thermal stability even after heating at 180 °C for 1 h. Furthermore, the two complexes exhibit a unique luminescent thermal stability.