Abstract: The mechanism of inducing quaternary amino groups on flax initiated by plasma has been studied. FTIR spectrum indicated that quaternary amino groups have been induced onto the flax. The effects of plasma initiatioin factors and chemical reaction conditions on modifying results were resear ched. The results show that the optimum technology conditions are that plasma power is 200 W, irradiation time is 150 s,the concentration of quaternary ammonium salt is 40 g/L,and NaOH is 15 g/L at 60 ℃ for 60 min.