Biodegradable composites made from bagasse fiber and biodegradable resin were prepared and the biodegradation were investigated by the soil burial test in terms of the effects of fiber content, alkali treatment to bagasse fiber and different soil. The biodegradable resin showed some extent biodegradation. The addition of bagasse fiber caused the acceleration of weight loss of the fiber reinforced composites in comparison with the neat biodegradable resin. The weight loss of the composites increased with the increase in the fiber content, which could attribute to the preferential degradation of bagasse fiber and the resin around the fiber. However there was no significant difference in weight loss between untreated and alkali treated fiber composites. Furthermore, it is noted that the weight loss drastically increased in the case of the composites buried in the microorganism enriched soil. This results from the increase of bacteria and fungi in soil. The photographs and SEM micrographs showed the degradation of the resin and the composites.