Abstract: Over 40% of the world's arable land are acidic soils, where aluminum toxicity stands as one of the primary obstacles limiting plant growth and productivity. Magnesium (Mg) is an essential nutrient for plants, being the most abundant free divalent metal ion within plant cells and participating in the regulation of plant resistance to abiotic stresses through various pathways. Given the similar hydration radii of Mg²⁺ and Al³⁺, Mg²⁺ compete with Al³⁺for binding sites on plant ion transporters and other vital biomolecules, thus alleviating the possible Al³⁺ toxicity. We searched the China National Knowledge Infrastructure (CNKI) and Web of Science core databases, a total of 79 articles published between 1989 and 2024 were retrieved on plant Mg-Al interaction research. In summary, exogenous Mg can effectively mitigate aluminum toxicity in plants grown in acidic soils, with the following mechanisms: ① Mg²⁺ competes effectively with Al³⁺ for binding sites on the plant plasma membrane; ② it effectively increases the secretion of plant organic acids; ③ it upregulates the expression of aluminum-induced Mg transporter genes, enhancing Mg uptake and aluminum tolerance; ④ it significantly enhances the plasma membrane H⁺-ATPase to promote the secretion of organic acids; ⑤ it boosts antioxidant enzyme activity, reducing reactive oxygen species (ROS) production and decreasing the risk of aluminum-induced oxidative stress; ⑥ it improves the activity of enzymes related to photosynthesis and carbon-nitrogen metabolism, alleviating photosynthetic impairments and source-sink imbalances caused by aluminum stress. Therefore, exogenous Mg nutrition (including Mg-containing fertilizers) plays a crucial role in enhancing plant resistance to aluminum toxicity. In addition, Mg plays a pivotal role in fundamental cellular metabolic processes in plants, such as maintaining proton pump activity in the plasma membrane and vacuolar plastids, influencing nitric oxide synthase activity and related gene expression, and significantly enhancing plant yield and quality in high-aluminum-toxicity farmland soils. Interestingly, in monocotyledonous plants like rice and wheat, millimolar concentrations of Mg²⁺ primarily alleviate soil aluminum toxicity by reducing the saturation activity of Al³⁺ at binding sites in the cell wall and plasma membrane. In dicotyledonous legumes such as soybean (Glycine max), cowpea (Vigna umbellata), and broad bean (Vicia faba), micromolar concentrations of Mg²⁺ can enhance the biosynthesis of organic ligands, mitigating soil aluminum toxicity. Adequate Mg nutrition not only promotes the formation of photosynthetic carbohydrates in plant leaves but also aids their transport to sink organs such as roots, maintaining source-sink balance. Future research should focus on three directions: firstly, integrating multi-omics technologies such as genomics, transcriptomics, and proteomics to deeply analyze gene expression profiles and proteomic changes under Mg and Al stress responses, comprehensively revealing the molecular regulatory network of Mg-Al stress interactions, and providing a theoretical basis for breeding aluminum-tolerant crops; secondly, exploring the impact of exogenous Mg nutrition (e.g., Mg-containing fertilizers) on the assembly processes and mechanisms of beneficial microbial communities in acidic aluminum-toxic soils; and thirdly, developing Mg-based soil conditioners and aluminum-tolerant crop breeding strategies to enhance crop tolerance to aluminum toxicity.