This study aims to isolate and purify polysaccharide from vinegar-baked Bupleuri Radix(VBRBP),and to preliminarily analyze its structural characteristics,and explore its synergistic anti-liver cancer activity in combination with chemotherapeutics.One homogeneous polysaccharide from vinegar-baked Bupleuri Radix was isolated and purified by water extraction and alcohol precipitation,membrane separation and cellulose chromatography.High-performance gel permeation chromatography,1-phenyl-3-methyl-5-pyrazolon pre-column derivatization,Fourier transform infrared spectroscopy,gas chromatography-mass spectrometry and nuclear magnetic resonance spectroscopy were used to identify the structure of VBRBP,and the inhibitory effect of its combination with different chemotherapeutics on the proliferation of HepG2 and Huh7 liver cancer cell lines was measured.The results showed that the homogeneous polysaccharide 5-1 from vinegar-baked Bupleuri Radix (VBRBP5-1) obtained through separation and purification was a neutral polysaccharide with a relative molecular weight of 30.78 kDa,composed of mannose,galacturonic acid,glucose,galactose and arabinose,with a molar ratio of 1.96∶2.38∶58.48∶22.85∶14.32.The backbone of VBRBP5-1 was composed of 1-α-D-glucose,1,6-α-D-glucose,1,4,6-α-D-glucose,1,4-α-D-glucose and 1,3,6-β-D-galactose residues,and the branched chain mainly contained 1-β-D-galactose,1,4-β-D-galactose and 1-α-L-arabinose,1,3,5-α-L-arabinose,1,5-α-L-arabinose residues. Combined administration of VBRBP5-1 could enhance the inhibition rates of 10-hydroxycamptothecine,methotrexate and cisplatin on hepatocellular carcinoma cells,showing a synergistic effect,in which the synergistic effect on cisplatin was superior to the others in these two hepatocellular carcinoma cells.In this study,the structure of VBRBP5-1 was analyzed and its synergistic anti-liver cancer activity was explored,which provided a reference for the interpretation of the structure-activity relationship and subsequent further development and utilization of polysaccharides from vinegar-baked Bupleuri Radix.