The work aims to study the correlation of fiber molecular structure, fiber morphology and paper strength by applying different beating mechanical effects on pulp fibers. The tensile related mechanical properties, such as tensile index, zero-span tensile strength and Z-direction tensile strength of the paper for different pulping time were measured. The fiber morphologies in the paper were observed by biological microscopy and scanning electron microscope. The functional groups, hydrogen bonds and crystallinity of the paper were analyzed by Fourier transform infrared spectroscopy and X-ray diffraction. With the increase of pulping time, the fiber molecular structure and properties of the paper firstly increased and then decreased. The fiber crystallinity, intermolecular hydrogen bond content, and tensile index of the paper all reached their maximum values at the 14th min, which were 79.63%, 43.64%, and 45.25 N.m/g, respectively. Within a certain range of pulping time, the tensile properties and molecular structure of fibers, such as crystallinity and intermolecular hydrogen bonds of the paper, show a trend of firstly increasing and then decreasing with the decrease of fiber size and the increase of brooming rate.