Abstract: Physiological process of germinating rice seeds is markedly influenced by the treatment of various concentrations of EMS ( ethyl methane sulphonate) after presoaking the seeds in water for 16—18 hours. The lower concentration of EMS stimulates the respiration and the activities of cytochrome oxidase and amylase, which associats with the higher rate of seed germination and seedling growth On the contrary, the inhibited effect is found by using the higher concentration of EMS (0.3—1.2%). The results show that the effects of EMS on the respiration and the activities of some enzymes of germinating seeds may be the important physiological cause of the chan es in germination, growth and root vigor of rice.