Abstract: The interface stress between bamboo fiber and matrix plays an important role in controlling the micro-mechanical behavior of bamboo vascular bundles. Based on the staggered alignment pattern and conical-end geometrical character of bamboo fiber, a modified shear-lag model was developed to study the stress transfer problem in bamboo vascular bundle sheath, with which the axial average stresses of bamboo fiber and fiber/matrix interface shear stress were derived. Then the effects of fiber-aspect ratio and fiber tip-length ratio on the stress distribution along the fiber length were investigated. The analysis results show that the large aspect ratio and sharp tapered-end of bamboo tiny fiber can make the interfacial stress transfer effectively.