To compare the effects of nitrogen fertilizer level on chlorophyll fluorescence characteristics in super hybrid rice flag leaves, a field fertilizer (slow release nitrogen) experiment was conducted with a super hybrid rice Y Liang you 1 as material. The photosynthetic electron transport rate (ETR), effective quantum yield (EQY), photochemical quenching coefficient(qP), and nonphotochemical quenching coefficient(NPQ) of flag leaves were measured at the heading, full heading, 10 d after full heading, 20 d after full heading. The results indicated that the ETR and EQY were increased from heading to 20 d after full heading, whereas, the NPQ decreased. During the same period, ETR, EQY, qP increased firstly and then decreased with increasing nitrogen level. The ETR and EQY at 135 kg/hm2 nitrogen level were the highest. In conclusion, the adaptive nitrogen amount for photosynthesis were 135-180 kg/hm2.