The third generation of mature Isoetes sinensis Palmer known as critically endangered species of ferns were used as materials by artificial breeding.With the method of pot cultivating,the paper examined the changing rule of membrane system,protective enzyme system and photosynthetic system under eight different herbicides in various agricultural region of origin,and explored herbicide pollution on the endangered I.sinensis Palmer’s physiology mechanism.Results showed that:(1)The relative electrolytic conductivity,MDA content,SOD activity and CAT activity of the I.sinensis Palmer leaves under different herbicide treatment in 15 d were significantly higher than that of control,while POD activity increased steadily before descending,and was near the compare level in 15 day;the photosynthetic system of I.sinensis Palmer leaves was severely affected.(2)The level of chlorophyll content under various herbicide treatments in 15 d was significantly lower than that of control.The stomatal conductance and transpiration rate increased dramatically,but net photosynthetic rate decreased obviously.The study found that I.sinensis Palmer is sensitive to all eight kinds of herbicides.Oxyfluorfen and MCPA-Na caused great damage on net photosynthetic rate,while fluazifop-p-buty,fenoxaprop-p-ethyl and bensulfuron -methyl caused great damage on membrane system.Herbicide is one of the important reasons of causing the I.sinensis Palmer to be endangered species.