Abstract: Chlorophyll fluorescence analysis is a commonly used technique to study plant photosynthetic physiology and to detect plant physical condition based on chlorophyll fluorescence parameters, including conversion efficiency (F_v/F_m) and potential activity (F_v/F_o) of photosystem (PS) at PSⅡ reaction center. To study the response of chlorophyll fluorescence parameters of Phragmites australis to irrigation using papermaking wastewater, the concentrations of heavy metal ions (Cr⁶⁺, Zn²⁺ and Cu²⁺) and chlorophyll fluorescence parameters in leaves of P. australis were observed. The P. australis plants were from Liaohe Estuary wetland, and irrigated with papermaking wastewater with concentration of chemical oxygen demand (COD_Cr) set to 50, 175 or 300 mg·L^-1. The results showed that irrigation using papermaking wastewater significantly affected the concentrations of heavy metal ions (Cr⁶⁺, Zn²⁺ and Cu²⁺) in leaves (P<0.05). The concentrations of heavy metal ions increased with the increase of COD_Cr concentration, and the greatest concentrations of Cr⁶⁺, Zn²⁺ and Cu²⁺ accumulated in leaves were respectively 2.80, 3.66 and 3.86 times as much as those in leaves with nonirrigation of papermaking wastewater. The accumulation of the three heavy metal ions in leaves varied in different growth periods. Cr⁶⁺ and Zn²⁺ mainly were accumulated in mature stage, and Cu²⁺ mainly accumulated in jointing stage. In addition, the concentration of COD_Cr in papermaking wastewater also influenced the chlorophyll fluorescence parameters. F_v/F_m and F_v/F_o were improved under irrigation using the papermaking wastewater with concentrations of COD_Cr 50 and 175 mg·L^-1. But when the concentration of COD_Cr was 300 mg·L^-1, F_v/F_m and F_v/F_o were reduced by 8.19% and 24.94% respectively, which illustrates that the function of PSⅡ reaction center was restrained. In conclusion, chlorophyll fluorescence parameters showed different responses to the three heavy metal ions. The values of F_v/F_o and F_v/F_m decreased with the increase of Cr⁶⁺ and Zn²⁺ concentrations, and increased with the increase of Cu²⁺ concentration. The F_v/F_m was significantly negatively correlated with Cr⁶⁺ concentration, while F_v/F_o was significantly positively correlated with Cu²⁺ concentration.