The influence of chemical modifications of banana fibres and fibre/PF composites fabricated by RTM technique was investigated by thermo gravimetric analysis (TGA). The kinetic studies of thermal degradation of untreated and treated fibres have been performed using Broido method. The treatment causes variation in the surface topography of the fibres. Therefore, more energy is needed for the degradation of fibres and hence higher activation energy for decomposition. Fiber reinforced composites with 40 wt% fiber loading was found to be more thermally stable. Furthermore, the treated fibre-reinforced composites with 40 wt% fiber loading posses superior thermal stability with respect to untreated fiber-reinforced composites; especially with the alkali treated fiber reinforced composites.