Abstract: Straw returning is a key technology for promoting green and low-carbon agricultural development and achieving the strategic goal of “chemical fertilizer reduction”. Its core value lies in the synergistic realization of nitrogen fertilizer reduction, crop yield increase, and improved nitrogen use efficiency. This article summarized the practical models of straw returning for nitrogen reduction in different major agricultural regions of China and elucidated the intrinsic mechanisms of “nitrogen reduction and efficiency enhancement” through multi-interface processes. Practical evidence demonstrated that region-specific models, such as deep ploughing in Northeast China, rotary tillage in the Huang-Huai-Hai region, and rapid decomposition in Southern China, when combined with optimized water and fertilizer management, could generally achieve a 15%-30% reduction in nitrogen fertilizer application for rice, wheat, and maize, while maintaining stable or even increased yields and improving nitrogen use efficiency. The core mechanism involved a multi-pathway synergistic coupling process: (1) Straw acted as a natural slow-release nutrient pool, directly supplementing and partially replacing nitrogen fertilizer, with release patterns better aligned with crop nutrient demand; (2) It enhanced soil organic matter and promotes aggregate formation, significantly improving soil structure and strengthening water retention, fertility preservation, and nitrogen immobilization capacity; (3) Exogenous carbon input drove the restructuring and functional activation of soil microbial communities, such as enhancing the abundance of nitrogen-fixing (nifH) genes and suppressing nitrification (amoA) activity, thereby optimizing carbon and nitrogen cycling and facilitating efficient nitrogen transformation and retention in the soil-microbial system; (4) The optimized rhizosphere microenvironment promoted root development and enhanced the activity of key enzymes, such as Rubisco and glutamine synthetase, in functional leaves, strengthening photosynthetic carbon assimilation and nitrogen metabolism efficiency; (5) Multiple pathways, including physical coverage, chemical adsorption, and biological immobilization, effectively reduced environmental risks such as nitrogen runoff, ammonia volatilization, and N₂O emissions. Future research should focus on the molecular mechanisms of straw-soil-microbe interactions, precise integration of regionally adapted technical models, comprehensive assessment of long-term ecological effects, and the development of intelligent decision-support systems to promote the large-scale and efficient application of straw returning technology in advancing green and high-quality agricultural development in China.