Abstract: Ge-Xian-Mi (Nostoc sphaeroids Kützing) grown in paddy fields is a rare edible cyanobacteria. The yield of wild resources of Ge-Xian-Mi has decreased owing to the extensive use of pesticides and fertilizers. The physiological toxic effects on Ge-Xian-Mi was lack of studies for bentazone, although it was a broad-spectrum and high-efficiency and low-toxicity new herbicide. This study compared and analyzed the physiological toxic effects in growth, oxidation and antioxidant system, photosynthesis and respiration of Ge-Xian-Mi treated by different times and different concentrations of bentazone. The results showed that bentazone inhibited the growth of Ge-Xian-Mi. In the wake of increased concentration and prolonged treatments for bentazone, they showed an upward trend as production rate of \rmO^-_2 and the content of H₂O₂, AsA, MDA, Pro and the activities of two antioxidant enzymes, CAT and POD in Ge-Xian-Mi. With the increased concentrations of bentazone, the content of GSH in Ge-Xian-Mi firstly decreased and then increased, but it was little changed overall. The SOD enzyme activity increased with concentrations and time treatments for bentazone, but the SOD enzyme activity was slightly less than 48h after treatment with high concentration of bentazone for 96h. After treated with bentazone for 72h, the total oxygen production and net oxygen production of Ge-Xian-Mi decreased with the increased concentrations of bentazone, however, no significant difference was found in respiratory oxygen consumption. The total oxygen production in the treatment of Ge-Xian-Mi was more easily inhibited by strong light and the recovery ability of weak light was reduced. The results of this study provide a reference for further research on the molecular mechanism of the toxicity and adaptation of Ge-Xian-Mi to bentazone and the ecological protection of wild Ge-Xian-Mi.