Currently, the sustainable development of global agriculture is facing multiple challenges, including soil degradation, resource constraints, and environmental pollution. With the continuous growth of the population and the increasing demand for food quality, improving soil health has become a crucial foundation for ensuring food security. Although chemical fertilizers play an important role in maintaining the high yields and high quality of plants, their excessive or unreasonable use can cause environmental problems, such as soil acidification and water eutrophication. Rhizosphere microbial communities play an essential role in plant nutrient acquisition, tolerance to environmental stress, and adaptation to environmental changes. Among them, synthetic microbial communities (SynComs) are designed via the targeted assembly of multiple microorganisms with well-defined functions and clear genetic backgrounds, enabling the achievement of complex functionalities that cannot be accomplished by single strains. They are powerful tools for deciphering the key interface interaction mechanisms among plants, soil, and microorganisms and play a vital role in promoting efficient utilization of plant nutrients, enhancing plant stress resistance, and increasing the efficiency and reducing the application of fertilizers. This study reviews the conceptual evolution, current research trends, and construction principles, methods, and tools of SynComs, and summarizes the role of SynComs in the sustainable development of agriculture from the aspects of promoting plant growth, inhibiting biotic and abiotic stresses, and improving and restoring soil health. Furthermore, this paper makes an outlook on the future research directions and emphasizes the research and development of targeted microbial agents, the application of artificial intelligence (AI) in community assembly, and the performance improvement of SynComs in field applications, aiming to support the coordinated and multi-objective development of food security, efficient resource utilization, and environmental protection through near-natural microbial means, thereby facilitating the green agricultural development of China.