We present a novel surface coating to resolve the stability of α-AlH_3. Inspired by the strong chemical adhesion of mussels, the polymerization of dopamine was first introduced to coat α-AlH₃ through simple situ polymerization. The α-AlH₃ was used as a substrate. In-depth characterizations confirmed the formation of polydopamine (PDA) on the α-AlH₃ surface. The coated α-AlH₃ sample was characterized by X-ray diffraction X-ray photoelectron spectrometry and Scanning Electron Microscope. The results show that a strong PDA film is formed on the surface of α-AlH₃, and PDA@α-AlH₃ retains its primary morphology. The crystal form of α-AlH₃ does not change after coating with PDA. The XPS analysis results show that N1 s appears on the material after coating with PDA, indicating that polydopamine is formed on the surface of α-AlH₃. The moisture absorption tests show that the moisture absorption rate of α-AlH₃ is greatly reduced after being coated with PDA. The excellent intact ability of PDA prevents α-AlH₃ from reacting with water in air. The thermal stability of α-AlH₃ before and after coating was analyzed by DSC. This work demonstrates the successful applications of dopamine chemistry to α-AlH₃, thereby providing a potential method for metastable materials.