AbstractBACKGROUNDIncreasing crop yield per unit area by increasing planting density is essential to ensure food security. However, the optimal combination of planting density and nitrogen (N) application for high‐yielding maize and its source–sink characteristics need to be more clearly understood.RESULTSA 2‐year field experiment was conducted combining three planting densities (D1: 70 000 plants ha−1; D2: 100 000 plants ha−1; D3: 130 000 plants ha−1) and three nitrogen rates (N1: 150 kg hm−2; N2: 350 kg hm−2; N3: 450 kg hm−2). The results showed that increasing planting density significantly increased leaf area index and grain yield but negatively affected ear traits. The Richards model was used to fit the dynamic changes of dry matter accumulation of maize under different treatments, and the fitting results were good. Increasing planting density increased population yield while limiting the development of individual plants, bringing the period of rapid dry matter accumulation to an early end and accelerating leaf senescence. An appropriate nitrogen rate could prolong the period of rapid accumulation of dry matter in maize, and increase the 100‐kernel weight. Increasing planting density enhanced post‐silking dry matter accumulation to a lesser extent, and the source–sink relationship of the maize population gradually developed from sink limitation to source limitation with increasing planting density.CONCLUSIONThe decrease in yield due to the insufficient source strength to meet the sink demand at too high densities was the reason that limited further improvement of the optimal planting density. An appropriate nitrogen rate facilitated the realization of yield potential at high density. © 2023 Society of Chemical Industry.