In rice the period of grain filling is characterized by transition of all vegetative organs from sink to source. A pot experiment was conducted to monitor variation of N and protein concentrations, N translocation and enzyme activities representative of nitrogen metabolism after the heading stage in different leaves and stem sections of two rice cultivars different in N use efficiency (NUE), high and low, treated with two levels of N fertilization. Compared with CK or Treatment N0, N application increased N concentration, soluble protein concentration and N translocation in leaves and stems. Nitrogen concentration in functional leaves decreased by 60-67% from heading to maturity, regardless of N rates, which indicates that N in grains comes mainly from leaves. However, N contribution rate from stems to grain depends on environmental N supply. N and soluble protein concentration and N translocation in leaves and stems was lower in Nanguang than in Elio at the maturity stage. Compared with CK, N application increased the activities of four N enzymes. And the activities decreased with the plant growth. The NR and GS activities were higher in Nanguang than in Elio, while NR activity depends more on N rate and growth stage. The GOGAT and GDH activities were lower in Nanguang than in Elio. NR and GS activities were significantly correlated to N and soluble protein concentrations at the heading stage and 2 weeks after the heading. All these indicate that higher NR and GS activities especially the latter, may predict the N status of rice, high N translocation and high NUE in rice.