Abstract: It is important for the production of rice with high yield and good quality according to plant nitrogen (N) content. In this experiment, transplanting density was set as the main plot (transplanting density of D1 and D2 was 18 and 25 hills m⁻², respectively), and N rates were set as the sub plots (N amounts of N0, N75, N105 and N135 were 0, 75, 105 and 135 kg hm⁻², respectively). The contents of total N and grain inorganic N, yield and quality of rice (Wuyoudao 4) were determined. The results showed that there was quadratic curve relationship between N fertilizer dosage and rice yield. The N application rate with highest yield was 113-119 kg hm⁻², the N application rate with maximum profit was 110-116 kg hm⁻². The N content of rice plants at each period, the contents of ammonium N and nitrate N of grain at the harvest period were increased significantly with the increase of N application amounts and were significantly different between N105 and N0 treatments (P < 0.05).The inorganic N content was significantly different between N105 and N135 treatments. There was an increased trend of grain protein content after N application, but their difference was not clear between treatments. The rice taste value was decreased with the increase of N dosage, and was decreased by more than 10% in N135 treatment (P < 0.05). Compared to low density, the yield of high density was increased by 11.4%. However, low density increased the concentrations of plant N, ammonium N and nitrate N of grain. The milled rice rate of low density was increased by 4.77 percentage point (P < 0.05) compared to high density, while the taste value was decreased. According to the fertilizer response function and the relationship between N rate and plant N content, the critical N concentration at jointing and heading stages was 15.26-16.18 g kg⁻¹ and 22.65-25.98 g kg⁻¹ in D1 treatment, and was 11.71-12.94 g kg⁻¹ and 20.73-23.24 g kg⁻¹ in D2 treatment, respectively. Increasing transplanting density was beneficial for high yield of rice, but excessive N was not. The optimal N rate was 91-105 kg ha⁻¹, and the suitable leaf N concentration was 24.82-25.98 g kg⁻¹ in D1 treatment and 22.18-23.24 g kg⁻¹ in D2 treatment at heading stage, which could be used as a diagnostic index for high yield and quality of rice.