Abstract: The objective of this research was to investigate the influence of bamboo fibers modified by impregnating with CaCO₃ nanoparticles on the adsorption situation of CaCO₃ particles and tensile properties of individual bamboo fiber as well as its composites. Effects of impregnated modification and in situ modification were compared. The results indicated that impregnated modification could make CaCO₃ particles which were good dispersion with uniform size fill the micropore and fold of the bamboo fibers to reduce manufacture defect. CaCO₃ loading reached 21.39%, tensile strength, modulus of elasticity and elongation of impregnated modified individual bamboo fiber increased significantly by 15.98%, 22.15% and 5.21%, respectively, but were below tensile properties of in situ modified fiber. By inspect and analysis to fracture morphology, the interfacial compatibility of composites which made from modified bamboo fiber and polypropylene film were improved. Tensile properties of the composites were enhanced accordingly. The tensile strength and tensile modulus of the composites reinforced with impregnated fibers increased by 6.95% and 15.80%, respectively, while the composites reinforced with in situ deposited CaCO₃ increased by 18.68% and 25.41%, compared to those reinforced with untreated fibers. In situ modification showed better improvement of mechanical properties both of individual bamboo fiber and composites. The process of impregnated modification was much easier.