AbstractBamboo is a natural bio-composite that has outstanding mechanical properties. Fibers are the structural building block of bamboo. Understanding the effect of fiber area on tensile properties of moso bamboo (Phyllostachys pubescens Mazei ex. H. Lebaie) will shed light on natural efficient design of bamboo. In this paper, fiber area and tensile properties of bamboo were tested on four bamboo slices, and a relationship found between fiber area and tensile properties. The results indicated that fiber volume increased exponentially in the radial direction from the inside to the outside of the culm wall. Bamboo tensile strength and MOE were linearly proportional to the fiber area. Fiber area also influenced bamboo fracture modes.