Bamboo fibers were used as reinforcement to prepare autoclaved aerated concretes and the fibers were modified by γ-（2， 3-epoxypropoxy）propyltrimethoxysilane（KH560）. The mechanical property results show that the autoclaved aerated concrete with 0.1% addition of modified bamboo fibers has 58.8% and 13.8% higher flexural strength（7 d） and compressive strength（7 d） than those without bamboo fibers， respectively. Fourier transform infrared spectroscopy（FTIR） and X-ray photoelectron spectroscopy（XPS） analysis show that the hydroxyl group of bamboo fibers react with the epoxy group of KH560， the characteristic peaks of Si—O bonds and Si element that emerged in modified bamboo fiber demonstrate that KH560 is grafted to the surface of the bamboo fibers， which improves the interface bonding between the bamboo fibers and the autoclaved aerated concrete matrix. X-ray diffraction（XRD） analysis indicates that a large number of Tobermorites with high crystallinity in the shapes of needle and sheet is formed in the hydration products and they interconnect with each other， forming solid networks. Scanning electron microscope（SEM） analysis also proves that the interfacial bonding is improved after the modification of bamboo fibers with KH560.