The property of cellulose microfibril reinforced natural rubber film was studied. Cellulose microfibril was prepared from banana powder (300 µm). The interconnected structure of cellulose microfibril having a diameter of 27 nm was observed by TEM. The effect of cellulose microfibril content (0.8-3.2 % wt) in the property of NR nanocomposite film was studied. Tear strength and thermal properties of the NR nanocomposite film is improved by increasing the cellulose microfibril content. Moreover, water absorption of the nanocomposite film is increased by increasing cellulose microfibril content. Increasing of cellulose microfibril content also enhances water permeation of nanocomposite films.