The natural bamboo fiber is a new kind of textile material. It is made from bamboo plant in physical ways. We studied the basic microstructure of natural bamboo fiber with the scanning electron microscope. The features of fiber length, the linear density and mechanical property were also analyzed. The degrees of crystallization and orientation were tested by diffractometer as well. The results showed that there were a lot of recesses and strips in the longitudinal direction, while the cross-section of the fiber was the shape of polygon with lumen in it. The length distribution arranged from 1.5mm to 215mm, the linear density was about 5.8dtex. The crystallization degree of the natural bamboo fiber was similar to the ramie fiber. In standard state, the breaking strength of the bamboo fiber was 6.71 cN/dtex, and the breaking elongation was about 3.48%, so the natural bamboo fiber was a kind of fiber with high strength and low extension. In hygrometric state, the tenacity and the elongation were both become larger.