AbstractDifferent hydrogen bond and crystalline cellulose structure models of eucalyptus fibers were studied by Fourier transform infrared spectrometer (FTIR), X-ray diffraction (XRD), and Cross-Polarization Magic Angle Spinning Carbon-13 Nuclear Magnetic Resonance (CP/MAS 13C NMR). It was shown that when the beating time was increased from 5 to 15 min., the content of inter-molecular hydrogen bonds, O(6)H···O3′, increased by 11.2% as measured by FTIR. However, the content of the inter-molecular hydrogen bonds decreased quickly as the beating time was increased from 15 to 25 min. Meanwhile, the contents of the intra-molecular hydrogen bond, O(2)H···O(6) and O(3)H···O(5), changed from 8.25% to 8.18% and from 39.33% to 31.27%, respectively, when the beating time increased from 5 to 15 min. The content of the intra-molecular hydrogen bonds increased quickly with the further increase in the beating time. It was shown by XRD that there was a little difference in the average width of crystallite size in the (002) lattice plane when the beaten time was between 5 to 25 min. Non-linear fitting of the cellulose C4 region of the 13C CP/MAS NMR showed that the average lateral fibril aggregate dimensions and the content of different cellulose polymorphs changed during beating.