Abstract. In the present paper, grafting of methyl methacrylate (MMA) onto flax fiber was carried-out under different reaction condition such as in air (IA), under pressure (UP) and under the influence of micro-wave radiations (MWR). Maximum percentage grafting (41.7%) has been observed in case of graft copolymerization carried-out in air at 55°C followed by grafting under pressure (36.4%) at 0.8 MPa and under the influence of microwave radiations (24.6%) at 210 W microwave power. Graft copolymers were characterized with FTIR spectroscopy, scanning electron microscopy (SEM), thermal analysis (TGA/DTA) and X-ray diffraction (XRD). Thermal stability of flax decreases on grafting under different reaction conditions. In case of XRD studies, cellulose crystals are better oriented in flax fiber followed by Flax-g-poly(MMA)-MWR, Flax-g-poly(MMA)-UP and Flax-g-poly(MMA)-IA.