Naked oat (Avena nuda L.) was originated from China, where soil nitrogen (N) is low availability. The responses of chlorophyll (Chl.) fluorescence parameters and leaf gas exchange to N application were analysed in this study. After the N application rate ranged from 60 to 120 kg ha-1, variable fluorescence (Fv), the maximal fluorescence (Fm), the maximal photochemical efficiency (Fv/Fm), quantum yield (ΦPS II) of the photosynthetic system II (PS II), electron transport rate (ETR), and photochemical quenching coefficient (qP) increased with N application level, however, non-photochemical quenching coefficient (qN) decreased. Moreover, there was no difference in initial fluorescence (Fo) with further more N enhancement. The maximum net photosynthetic rate (Pmax), apparent dark respiration rate (Rd) and light saturation point (LSP) were improved with 40-56 kg N ha-1 as basal fertilizer and 24-40 kg N ha-1 as top dressing fertilizer applied at jointing stage. Initial quantum yield (α) was decreased with 24 kg N ha-1 as basal fertilizer and 56 kg N ha-1 as top dressing fertilizer. Flag-leaf net photosynthetic rate (Pn) was significantly enhanced at the jointing and heading stages with 40-56 kg N ha-1 as basal fertilizer; in addition, increased at grain filling stage of naked oat with 40-56 kg N ha-1 as top dressing fertilizer. 90 kg N ha-1 (50-70% as basal fertilizer and 30-50% as top dressing fertilizer) application is recommended to alleviate photodamage of photosystem and improve the photosynthetic rate in naked oat.