57 rice varieties mainly planted in the middle and lower reaches of Yangtze River were used to study the physiological and biochemical characteristics of nitrogen efficient rice varieties mainly planted in this region.Hydroponic culture was conducted to screen the nitrogen efficiency of rice.The nitrogen-efficient and nitrogen-inefficient rice varieties screened were further used to analyze the differences in growth， yield formation， absorption and utilization of nitrogen， activity of enzymes， metabolites， and expression level of related genes with hydroponic culture， soil pot， and field trials.The results showed that the nitrogen efficient and nitrogen inefficient rice variety was determined to be Quanyousimiao（5#） and Wuyoujingsimiao（8#）.5# had better root architecture and biomass under both +N and -N treatments， with significantly higher plant height， root length， number of root tips， total surface area and volume of roots， and dry weight of roots and shoots compared to that of 8#.The effective number of spikes， spike length， thousand-grain weight， seed setting rate， grain yield， and absorption and utilization of nitrogen of 5# was higher than that of 8#.The content of nitrogen， accumulation of roots and shoots， the absorption of ¹⁵NO₃^- and ¹⁵NH₄⁺， nitrogen utilization index， and distribution ratio in grains of 5# was significantly higher than that of 8#.The expression level of most genes involved in the absorption， transport， reduction， and assimilation of nitrogen in 5# was significantly higher than that in 8#.The activity of NR in root and activity of GOGAT in shoot， the content of soluble protein and sugar in 5# was significantly higher than that in 8#.It is indicated that excellent architecture of root， stronger absorption capacity of nitrogen， efficiently transporting nitrogen to shoot， timely reducing and assimilating nitrogen， and distributing more nitrogen to grains are important characteristics of nitrogen-efficient rice variety.