In this experiment, poly(butylene adipate-co-terephthalate) (PBAT)/starch composites were prepared. The effects of several surfactants on the mechanical properties of the composites were compared, and the best surfactants were selected to study the effects of their dosage on the properties of the composites. The mechanical properties, melt flow, hydrophilic and thermal properties of PBAT/starch composites were analyzed, and the molecular structure and microstructure morphology of the composites were characterized by infrared spectroscopy and polarization microscope. The results show that sodium dodecylbenzene sulfonate (SDBS) has a better modification effect on starch. When the dosage of SDBS is 15 g, the tensile strength of the composite is 10.15 MPa, and the elongation at break is 639.49%. With the increase of SDBS, the melt flow rate of composites first decreases and then changes little, the hydrophilicity increases, and the crystallization temperature increases, but the effect on the melting temperature is not significant. Polarization microscopy shows that the crystal refinement and the size decreases. Infrared characterization shows an increasing trend in the intensity of the response peak at 3 340 cm^-1.