AbstractBamboo (Sinocalamus affinis) lignophenols (Lps), synthesized using a phase separation system, were used as a natural plasticizing additive to complex with pulp (short fiber and fluffy short fiber) sheets. The structural features of Lps were analyzed by gel permeation chromatography (GPC), Fourier transform infrared (FT-IR) spectroscopy, and proton-nuclear magnetic resonance (1H-NMR). The pulp sheet absorptivity of Lps, as well as the physical properties of complex sheets, were discussed. Results showed that when the concentration of bamboo Lps solution was 10 g/L, the absorption amount of Lps in the sheets made up of short pulp fibers (12%) was slightly higher than that of sheets made of fluffy short pulp fibers (10%), whilephysical properties, such as tightness, tensile strength, elongation, bursting, and tearing, were improved obviously after the addition of Lps. More obvious improvement in the physical strength was found in sheets made up of fluffy short pulp fibers. Results indicated that the amount of absorbed Lps was of the same importance as the properties of the pulp fibers. It is necessary to adjust the properties of both the Lps and sheets to get the best mechanical strength for the pulp sheets.