Abstract: Developing green manure–maize rotation systems is a pivotal strategy for simultaneously securing maize yield, reducing and optimizing chemical fertilizer use, building soil fertility, and protecting farmland ecology. We synthesize the yield-increasing and fertilizer-saving effects of green manure–maize rotation and their underlying mechanisms, and quantifies the development potential of this system in China. Results from 21 multi-site long-term experiments conducted during 2008–2024 showed that, relative to conventional nitrogen (N) fertilization, green manure-maize rotations increased grain yield by 7.6%, 3.8%, and 3.9% under 0%, 15%, and 30% reductions in N application, respectively. Even without chemical N fertilizer application, maize yield under green manuring still reached 92.7% of that under the conventional fertilization. We elucidate the mechanisms underlying the yield-increasing and fertilizer-saving effects from three perspectives: enhancing maize nutrient acquisition and utilization, improving soil health, and strengthening agroecosystem services. Utilization of green manure with reduced fertilizer optimizes yield components, promotes nutrient uptake, and improves fertilizer use efficiency. Long-term green manuring enlarges soil C and N pools. Soil organic matter and total N rose by 0.45 and 0.13 g/(kg·yr), respectively, at the condition of green manure combined with 85% of the conventional N rate. Green manure–maize rotation reduces net global warming potential, curbs N losses, mitigates wind and water erosion, and boosts the resilience of maize systems to extreme weather. The potential area for green manure–maize rotation in China is estimated at 6.22 million hectares, yet the average area in 2022–2024 was only 0.56 million hectares, only accounting for 9.0% of the potential area, indicating vast room for expansion. The system is currently distributed in North China and the dryland regions of Southwest and South China. Suitable green manure species, sowing management, and incorporation practices for each region are summarized, and the constraints on green manure development and policy recommendations are delineated. Future priorities include continued technological integration, mechanism-oriented research, and theoretical innovation to underpin large-scale adoption of green-maize rotation systems.