Abstract: Using surfactants to improve the particle size of Arctium lappa L. polysaccharides, and the optimal process conditions were obtained by single factor and response surface method. The structure of Arctium lappa L. polysaccharides before and after improvement was characterized by UV, Fourier transform infrared spectroscopy (FT-IR), particle size, and scanning electron microscopy. The results showed that the optimal process conditions for improving the particle size of Arctium lappa L. polysaccharides were as follows: The surfactant was Tween-80, the concentration was 0.5%, the vortex time was 16 s, and the pH was 5.67, under these conditions, the particle size of Arctium lappa L. polysaccharides was 6.19±0.14 nm. FT-IR analysis showed that the modification with surfactants did not change the structure of Arctium lappa L. polysaccharides. The UV spectrum showed a slight fluctuation at 280 nm, which might be attributed to the UV absorption of surfactants in this wave band. The particle size analysis showed that the grain size of improved Arctium lappa L. polysaccharides decreased significantly compared with unimprovement. The scanning electron microscopy results showed that the improved Arctium lappa L. polysaccharides exhibited a more ordered spherical structure and more uniform sizes. This study can provide a theoretical basis for the preparation of a polysaccharide system with controlled particle size.