Measurements and analysis of chlorophyll fluorescence can reflect changes in plant leaf photochemical efficiency and have been increasingly used in plant ecological monitoring. This study used the Mencheng Lake wetland park, supplied with reclaimed water, as a study area, and Phragmites australis, Typha angustifolia and Zizania latifolia as typical emergent plants. We studied the chlorophyll fluorescence response characteristics of plants under different total nitrogen gradient by measuring leaf-scale chlorophyll fluorescence parameters outdoors and the corresponding water total nitrogen content indoors. Minimal fluorescence (F_o) and maximal fluorescence (F_m) were increased and nitrogen content in water was elevated. Maximum quantum efficiency of photochemistry in photosystem II in the dark (F_v/F_m) and quantum efficiency of PSll (ΦPSll) affected by nitrogen increased at first and then plateaued when nitrogen content reached the 15 to 20 mg·L^-1 interval. Photochemical quenching (qP) tended to decrease after the first increase, but nonphotochemical quenching (NPQ) changed without obvious regularity. When water total nitrogen content was at the 15-20 mg·L^-1 level, photochemical reaction was abated and photosynthesis was inhibited. Also, fluorescence parameters of different types of emergent plants were not the same; photosynthesis was significantly stronger in the growth stage (June) than the mature stage (September).