Abstract: The effects of Cu and As(Ⅴ) and their compound pollution on the growth, bioaccumulation capacity and superoxide dismutase (SOD) activities of Hydrilla verticillata (L.f.) Royle (H. verticillata) were studied by indoor simulation experimentation. The results showed that the 4 d-EC₅₀ of Cu and As(Ⅴ) for H. verticillata was 2 and 12 μmol/L, respectively. Cu was more toxic to this plant than As(Ⅴ). Compared with the control treatment (0 μmol/L Cu + 5 μmol/L As(Ⅴ)), the growth of the plant was promoted when exposed to lower concentrations of Cu (< 2 μmol/L) + 5 μmol/L As(Ⅴ), and the accumulation of total arsenic as well as As(Ⅲ) (which accounted for most of the total arsenic) also dramatically decreased. Moreover, the addition of As(Ⅴ) also inhibited Cu accumulation and increased SOD activities of H. verticillata, as compared with the Cu single treatment. As a result, it appeared to have an antagonistic effect for lower concentrations of Cu + 5 μmol/L As(Ⅴ). Although As and Cu accumulation were markedly inhibited at higher Cu concentrations (≥2 μmol/L) + 5 μmol/L As(Ⅴ) in comparison with the single treatment, the growth of the plant was considerably inhibited. Additionally, SOD activities of the plant were strongly reduced (P<0.05) by the compound pollution of Cu + As(Ⅴ) as compared with the single pollution. Therefore, higher concentrations of Cu + 5 μmol/L As(Ⅴ) presented a synergistic effect on H. verticillata. In summary, this plant has high potential to be used for the phytoremediation of waters contaminated by Cu and As and their compounds at relatively low concentrations.