Abstract: The interface of bamboo fibers(BF) reinforced polylactic acid(PLA) composites was regulated by hydroxide and isocyanate, and BF/PLA composites were prepared by injection molding process. The thermal aging properties of BF/PLA composites were studied by the methods of FTIR, XRD, gel permeation chromatography (GPC) and SEM. The results show that the C O in the molecular chains of PLA are continuously hydrolyzed, the C—O in the molecular chains of PLA are fractured and generated the PLA of smaller molecular weight and lower polymerization degree, the crystallinity degree of PLA is reduced, the bonding interface between BF and PLA is destroyed, the tensile strength and impact strength gradually decrease with the increasing of aging time in the thermal aging process. The tensile strength and impact strength of the BF/PLA composites reduce by 75% and 77.6% after thermal aging at 80℃ for 16 days, while the tensile strength and impact strength of the BF/PLA composites reduce by 80.3% and 83.4% after thermal aging at 100℃ for 32 h. The effect made by temperature on the aging property of BF/PLA composites is significant, the higher the temperature, the faster the aging.