At 0 ℃ low temperature stress,the dynamic process of protective enzyme system (POD,SOD and CAT),osmotic regulation substances (soluble sugar and soluble protein) and malondiadehyde (MDA) as well as relative electric conductivity were determined in Isoetes sinensis Palmer submerged leaves.The results showed that the relative electric conductivity,soluble sugar and activity of CAT increased at the beginning then decreased.The SOD activity gradually increased with the process of low temperature stress.The activity of POD,soluble protein and chlorophyll content decreased in the whole process of low temperature stress.MDA content were lower than the control group during the whole low temperature stress process and fluctuated within a certain range.We can concluded that the I.sinensis Palmer submerged leaves were negatively influenced by 0 ℃ low temperature stress,but the osmotic regulation substances,protective enzyme system,plasma membrane permeability could adjust themselves to avoid low temperature harms,which led to some tolerant ability of I.sinensis Palmer to the low temperature condition.