Abstract: Increasing planting density is one of the major agronomic practices to achieve high grain yield in maize.However,high plant populations can lead to poor root growth which can limit nutrient acquisition.Therefore,constructing an efficient root system is essential for improving crop productivity and nutrient use efficiency simultaneously.In the study,a density-tolerant maize cultivar Kenwo 1 was adopted,and split plot was designed.Main plot was planting density including 60 000plants·hm^-2（D6） and 80 000 plants·hm^-2（D8）,respectively.In sub-plot,two chemical nitrogen fertilizer application patterns were applied.Chemical nitrogen fertilizer was 100%applied as base fertilizer,which was abbreviated as N1T1.Chemical nitrogen fertilizer was split-applied as base and sidedressing N,which was abbreviated as N2T2.Farmers’practices,in which chemical nitrogen fertilizer was 100%one-time application,was conducted as control （CK） without deep tillage during the seedling stage.By comparing with farmers’practices （CK）,D8N2T1 improved root length per plant,root biomass,root surface area,specific root length,nodal root number and root growth in 0-60 cm by11.4%,22.0%,11.2%,13.1%and 10.9%,The root length of 0-60 cm soil depth increased by 11.3%-44.6%,respectively.Meanwhile,nitrogen accumulation per population,N remo-bilization efficiency,partial nitrogen productivity （PFP）,and nitrogen agronomic efficiency （AE） increased by 71.1%,51.6%,102.4%and 143.1%.Grain yield of D8N2T1 was 17.1 t·hm^-2,which increased by 50.6%.In conclusion,increasing planting density matching with"side-and deep-"＆split-N application could collectively increase grain yield through optimizing root growth,improving nitrogen accumulation and remobilization.