Abstract: Both nitrogen nutrition and cultivation density regulate rice population composition, synchronized N nutrition and density could improve rice population productivity and nitrogen use efficiency greatly. We reviewed the main achievements of the researches, especially those under nitrogen reduction and dense planting conditions. Nitrogen reduction and dense planting help the formation of satisfactory population structure of rice, thus promoting rice population productivity and fertilizer use efficiency, and N reduction and dense planting have positive synergistic interaction. We verified the effect of “extremely dense planting” technique through field experiments in multiple sites for many years, with a target rice yield 9000 kg/hm² under a moderate soil fertility condition. The main core of the technology package for the “extremely dense planting” included increasing seedling transplanting density as high as 400×10⁴ hm² (rice cultivar ‘Nanjing 46’), reducing nitrogen application rate to 90 kg/hm², no tillering fertilizer but heavy heading fertilizer. Companied with the conventional planting, the “extreme dense planting” mode limited tillering, coordinated rice population growth and main stem panicle formation, the rice yield therefrom were significantly increased and nitrogen fertilizer use efficiency was improved. The tillering number under the extremely dense planting mode were only 1.2 per plant on average, but the unit effective number of panicles, 1000-grain weight and the grain setting rate were increased significantly, thus the rice yield were increased by 27.4%, and the agronomy efficiency of nitrogen fertilizer by 120%. For the widely population of the “extremely dense planting” technology, the suitable N rate and planting dense combination need approaching under different rice cultivars, cultivation modes, nitrogen reduction rates, and soil type and fertility levels. The emerging rice drone aerial seeding technology is accepted because of high-density and precise seeding, that may affect the nitrogen-density interactions. In spite of the success in practice, the specific physiological and molecular regulatory mechanisms as affected by extremely dense planting are not very clear, more studies needed to ensure the stable and sustainable widespread application of “extremely dense planting” technology of rice.