Abstract: Nano-fertilizers refer to a new type of fertilizer produced using nanotechnology, which has structural or functional unit sizes at the nanometer level (1−100 nanometers) or employs nano-carriers to deliver nutrients. Nano-fertilizer products are diverse, with nutrient elements distributed in various forms such as crystalline particles, pore structures, and interfacial assemblies. In China, nano-fertilizers primarily include nano-structured fertilizers, nano slow/controlled-release fertilizers, nano-carbon enhanced fertilizers, and nano-biofertilizers. Nano-structured fertilizers are novel fertilizers produced by processing nutrient elements (macro-elements such as nitrogen, phosphorus, and potassium, or micro-elements such as boron, zinc, and selenium) into particles with sizes ranging from 1 to 100 nm through physical pulverization, chemical synthesis, or biological assembly technologies. Nano slow/controlled-release fertilizers are a new type of fertilizer created by mixing traditional fertilizers with nanometer- or submicron-scale materials (e.g., nano-zeolite, nano-kaolin, and mesoporous nano-silica) as carriers, imparting slow-release properties to the traditional fertilizers. Nano-carbon enhanced fertilizers are functional fertilizers prepared by combining carbon nanomaterials such as carbon dots, graphene, and carbon nanotubes with essential plant nutrients, offering good biocompatibility and application potential. Nano-biofertilizers integrate live microorganisms such as fungi and bacteria or their extracts with nanoparticles, reducing and encapsulating metal ions under mild conditions to form nanoparticles. Compared to traditional fertilizers, nano-fertilizers possess distinct advantages in several aspects. Their small size, high specific surface area, and excellent slow-release properties enable them to enhance the efficiency of plant nutrient absorption and utilization, minimize soil nutrient loss, and mitigate environmental pollution. These benefits manifest in several ways: boosting photosynthesis by increasing chlorophyll content, optimizing photosystem functionality, and activating ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) activity; precisely regulating nutrient metabolism through the activation of key enzyme systems and hormonal signaling networks, thereby significantly improving nitrogen and phosphorus utilization efficiency; enhancing stress resistance by modulating antioxidant enzyme systems, maintaining ion homeostasis, and activating osmoregulatory substances to effectively mitigate salinity, drought, and pest stresses; and improving soil properties by increasing microbial diversity, enhancing enzyme activity, and immobilizing heavy metals to enhance soil physicochemical characteristics. Despite their advantages, nano-fertilizers face certain limitations in practical application and require further research and optimization. Future research endeavors should focus on the following directions: firstly, addressing the urgent need to reduce the cost of nano-fertilizer production and facilitate its industrial application; secondly, integrating crop, soil, and climate data to build machine learning models that dynamically recommend optimal application rates, thereby achieving on-demand nutrient supply. Thirdly, establishing an environmental risk assessment and early-warning system, and training machine learning models based on nanoparticle physicochemical properties and monitoring data to predict ecological risks and enable automatic alerts. These studies will not only provide a new theoretical foundation for a deeper understanding of nano-fertilizer applications in agriculture and forestry but also offer crucial technical support for achieving sustainable development in these sectors.