In 2017-2018, a field experiment of rape-early rice-late rice in red paddy field was conducted in triple-cropping areas (Jinxian of Jiangxi) in the middle reaches of the Yangtze River, to study the effects of higher planting density and lower nitrogen rate with straw returning on crop yield and soil nitrogen storage of red soil with different fertility, providing a reference for the development of resource conservation and environment-friendly production technology in the triple cropping system area. The results showed that under the condition of returning three crop straws to the field, increasing of soil fertility and planting density could significantly promote the increasing of growth and yield of both rice and rapeseed. The treatment of 30% higher planting density with 20% lower nitrogen application rate could meet the nitrogen demand of the three crops growth, ensure the normal growth of the crops, and significantly improve the nitrogen utilization rate. In general, the crops yield of the treatment of high planting density combined with low nitrogen rate could reach or even slightly higher than that of the conventional cultivation, especially under the condition of high fertility. In the short-term, high planting density combined with low nitrogen rate cultivation did not significantly reduce the total content and storage capacity of both total nitrogen and alkali nitrogen in plough layer soil, but significantly reduced the alkali nitrogen content and the storage capacity of the plough layer soil under the condition of low fertility.