The effects of butachlor on the physiological activity and cell metabolizable products of Nostoc sphaeroides were focused in this study. After exposure to the different concentrations of butachlor

it was found that photosynthetic rate

respiration rate

and photosystem Ⅱ activity improved when the concentration of butachlor below 5 mg·L-1

however

the reverse results were obtained when the concentration of butachlor was above 5 mg·L-1. Meanwhile

the structure and biological function of the Nostoc sphaeroides were destructed under stress

the permeability of plasma membrane of Nostoc sphaeroides increased as well as the contents of MDA and O2 with the concentration of butachlor increasing. While the content of crotenoids increased and the activity of SOD improved to resist the damage of batachlor when Nostoc sphaeroides was exposed to low concentration of butachlor. But for the actual using concentration

this resistance was quite limited

so it is necessary to limit the use of butachlor in order to protect the habitat of Ge-xian-mi.