We report the preparation of polybutylene succinate (PBS)/sisal-fiber (SF) composites. The effects of mixing temperature and of steam-explosion pretreatment of SFs on the mechanical properties of the composites were investigated, and the mechanism of action was studied by infrared spectroscopy, scanning electron microscopy, and x-ray photoelectron spectroscopy. The results indicate that as the mixing temperature increases, PBS flows better and can graft onto steam-exploded sisal fiber (SESF), the interfacial bond property between SESF and PBS improves, and the mechanical properties of the composites improve. The mechanical properties of the composites are maximal for a mixing temperature of 200 degrees C. The results also demonstrate that the cellulose content and the specific fiber surface area can be increased by steam-explosion pretreatment, so that the mechanical properties of the composites can be improved. POLYM. ENG. SCI., 51:474-481,2011. (C) 2010 Society of Plastics Engineers