Bupleurum chinense DC., customarily called “Bei chaihu” in China, is a well-known traditional Chinese medicine distributed mainly in the northern region of China [1]. B. chinense is an important “harmony” herb, which can balance different organs and energies within the body, and it is also used as a tonic herb because of its ability to strengthen the action of the digestive tract, improve liver and circulatory system function, and relieve liver tension. However, the physicochemical characterization and pharmaceutical effects of bioactive polysaccharides from B. chinense have not been extensively studied. Therefore, the present studies were carried out to isolate and purify the polysaccharide fractions from B. chinense and further investigate their basic physicochemical characterization and antioxidant capacity. In the present study, the yield of the crude water-soluble polysaccharide extracted from B. chinense was 12.4% of dried material. After the freeze–thaw process and deproteination by a combination of proteinase and the Sevag method, the crude polysaccharide sample (WBCP) was further purified by AKTA Explorer purification with ion exchange chromatography and gel filtration chromatography. First, WBCP was loaded onto a DEAE-cellulose column eluted with de-ionized water and a 0 1 M gradient of NaCl solution. The main fractions eluted by de-ionized water and NaCl solution were collected, lyophilized, and further fractionated on a Sepharose CL-6B column eluted with 0.15 M NaCl solution. Three main fractions (WBCPa, WBCPb, and WBCPc) were separated for further analysis of physicochemical properties and antioxidant activities. Their chemical and physical characteristics were determined by chemical methods, gas chromatography (GC), and high-performance gel-permeation chromatography (HPGPC). The results of total sugar, protein, and uronic acid contents, molecular weight, and monosaccharide compositions of the polysaccharide fractions are summarized in Table 1. All the polysaccharide fractions, WBCPa, WBCPb, and WBCPc, appeared as pale yellow powders. The results using the phenol-sulfuric acid colorimetric method showed that the polysaccharide fractions WBCPa and WBCPc had a higher total carbohydrate content (98.1% and 99.2%, respectively) than WBCPb (95.7%). They showed a negative response in the Bradford assay. In addition, no absorption at either 280 or 260 nm was detected by UV spectrophotometer, which indicated the absence of protein and nucleic acid. Furthermore, based on the m-hydroxydiphenyl method, the uronic acid content of WBCPc was 33.5, while uronic acid was undetectable in both WBCPa and WBCPb. The average molecular weights of WBCPa, WBCPb, and WBCPc calculated by HPGPC were 103.7, 54.6, and 77.4 kDa, respectively. According to GC analysis, both of the neutral fractions, WBCPa and WBCPb, were composed of mannose, galactose, and glucose with molar ratios of 0.6:2.4:3.2 and 0.2:1.6:4.8, respectively, while the acidic fraction, WBCPc, was composed of mannose, glucose, and galacturonic acid with a molar ratio of 2.5:1:2.2.