[Background and Aims] Among agricultural fertilizers, nitrogen (N) is the most essential nutrient for the growth, productivity, and grain quality of winter wheat (Triticum aestivum L.).The aboveground N-uptake (AGN) at maturity is positively associated with wheat grain yield.Efficient N uptake from fertilizer and soil sources enhances the plant N-use efficiency (NUE) and reduces the leaching of nitrate to deep soil.However, the responses of NUE, N uptake efficiency (UPE) and N utilization efficiency (UTE) to plant density and how the root distribution and N-uptake at different soil depths is affected by plant density is largely unknown.[Materials and Methods] During the 2010-2011 and 2011-2012 crop seasons, two winter wheat cultivars (Tainongl8 with lower tillering capability at plant densities of 135, 270, 405 and 540 plants m2 and Shannongl5 with higher tillering capability at plant densities of 90, 172.5, 345 and 517.5 plants m-2) were evaluated to investigate the effect of plant density on grain yield, NUE, UPE and UTE.15N-labeled urea was injected into soil at depths of 0.2, 0.6, and 1.0 m under each plant density to elucidate N uptake at different soil depths as affected by plant density.[Results] Significant synchronous increases in grain yield, NUE, UPE, absorbed N from fertilizer (Nf) and soil (Ns) and significant root length density (RLD) and 15N uptake increases at each soil depth, as well as a significant reduction in UTE, were observed as the plant density increased from 135 to 405 plants m-2 for the cultivar T18 or from 90 to 172.5 or 345 plants m-2 for the cultivar S15.Furthermore, the increased RLD in deep soil had greater effects on N uptake than RLD increase in top soil.Increasing plant density enhanced N uptake of winter wheat and therefore increased UPE.NUE was positively correlated with UPE but not with UTE, indicating that optimising the seeding rate improved NUE mainly by raising UPE due to increased AGN as a result of optimised RLD and a synchronous increase in Nf and Ns.[Conclusions] Increasing the plant density increases AGN primarily by increasing the RLD in deep soil and the plant density could be a factor useful to obtain higher grain yield and NUE in winter wheat and to efficiently recover N leached to deep soil.