The precise characterization of the microstructure of bundle is essential for an accurate determination of their properties and behavior. This paper presents a study on the microstructure of continuous fiber bundles by Serial Sectioning Method. Bundle is firstly cured by resin to keep the fiber spatial configuration in the bundle. A series of cross-section images vertical to the bundle direction are captured and polished enough to take digital photographs by the Charge-coupled Device (CCD) microscope. A 3D solid microstructure of the bundle is implemented by linking the correspondent circle for separate fiber in the 3D solid software Pro/E. Reconstructed bundle structure truly represents the spatial configuration of the fibers in the bundle.