Acetic anhydride, as a kind of acylation reagent, was grafted on the surface of chitin whisker (CHW) to obtain acetylated CHW (ACHW). The structure and morphology of the ACHW were characterized by FT-IR, XRD, and TEM. A series of poly (butylene succinate) (PBS) composites (PBS/CHW, PBS/ACHW) were prepared with mass fraction of 0, 1%, 3%, 5%, and 7% of CHW or ACHW, and PBS by melt-mixing method. The crystallization property, thermal stability, and mechanical property of the composites were investigated. The dispersion of CHW and ACHW in PBS/CHW and PBS/ACHW were also observed by ESEM. The results indicated that the interfacial compatibility between ACHW and PBS had been effectively improved by the introduction of the ACHW. ACHW can act as nucleating agent and increase the crystallization rate of PBS, during the crystallization process of PBS. But it did not change the crystalline form of PBS. Additionally, when the mass fraction of 3% of ACHW was added into the PBS, the thermal stability of PBS/ACHW composite was significantly increased, the temperature at 5% mass loss (Td-5%) and the peak of pyrolysis temperature (Td-max) was 349.2 ℃ and 401.9 ℃, Td-5% and Td-max increased by 53℃ and 33.6℃ comparing pure PBS, respectively. The comprehensive mechanical properties of PBS/ACHW-3 were optimal and the tensile strength of the film increased from 30.9 MPa to 35.8 MPa, the elongation at break increased from 9.8% to 17.5%.