Magnesium (Mg) is an essential mineral element for plants, playing critical roles in photosynthesis, nutrient transport, stress responses, and nutrient use efficiency. However, the long-term ignorance of Mg fertilizers in China's agricultural production has led to widespread soil Mg deficiency, which constrains crop yield, quality, and the potential for further improvement in nutrient use efficiency. This study provides a comprehensive assessment of soil exchangeable Mg status and Mg fertilizer use in China, based on integrated data from national surveys and field experiments conducted by the National Mg Network. It also evaluates the effects of Mg fertilizers in improving crop quality and nutrient use efficiency. In addition, it analyzes the national demand and usage of Mg fertilizers, thereby advancing the understanding of the fundamental physiological functions and agronomic roles of Mg in crop production. Survey results indicate that soil exchangeable Mg concentrations are generally higher in the northern regions (average 271.7 mg kg-1) compared to the southern regions (174.6 mg kg-1). The application of Mg fertilizers remains below 9%, with application rates far below than crop requirements. Mechanistic studies demonstrate that Mg directly participates in the light reactions of photosynthesis and carbon fixation, and regulates the circadian rhythms of photosynthesis. It also promotes nitrogen uptake and assimilation through improved carbon allocation and signaling pathways. Moreover, Mg exhibits multiple protective mechanisms under aluminum toxicity, salinity, and high-temperature stress, and activates plant immune responses to enhance disease resistance. Field trials show that appropriate Mg application can increase average crop yield by 14.6%. It also significantly improves the nutritional and sensory quality of agricultural products while improving the efficiency of nitrogen, phosphorus, and potassium fertilizer use. The estimated Mg fertilizer demand in China's agricultural production is 2.81–4.40 million tons (as MgO), yet the current application of Mg fertilizer is just 150000 tons. The insufficient development and diversification of Mg fertilizer products remain a major bottleneck for the green development of Chinese agriculture. In the future, it is necessary to strengthen the basic and applied research on plant Mg nutrition, expand the production and supply chains of Mg fertilizers, and enhance policy support to promote large-scale adoption. These efforts will contribute to higher yield, better quality, improved nutrient use efficiency, and the sustainable development of Chinese agriculture.