Abstract: Alkali pretreatment, hydrothermal pretreatment, and H₂O₂ pretreatment was developed to pretreat the Dendrocalamus sinicus, which is the largest bamboo species distributed in Southwest China. The objective of the present research was to evaluate the effect of pretreatments on the accessibility and thermoplasticity of bamboo fiber during sulfonation modification. It was demonstrated that 3 pretreatments could obviously improve the accessibility of sulfonation reaction, and a maximum of 0.49 mmol/g was achieved as the bamboo powder was pretreated with H₂O₂ which had the highest degree of sulfonation modification. In addition, the plasticity of bamboo fiber was improved with the increase of sulfonic group content after sulfonation. The DSC analysis results revealed that the thermoplasticity of bamboo fiber was significantly improved under the synergistic effect of H₂O₂ pretreatment combined with sulfonation modification, and its glass transition temperature (T_g) was 104.71 ℃.