OBJECTIVE： To screen and characterize effective components of immunopotentiating activity in Senecionis cannabifolii Herba. METHODS： The polysaccharide components were obtained by water extraction and alcohol precipitation method to yield 50％ alcohol precipitation sample （SCHE-1） and 80％ alcohol precipitation sample （SCHE-2）. The cells from mice mononuclear macrophage line RAW264.7 were divided into blank group （medium without serum）， negative control group （medium with serum）， lipopolysaccharide group （LPS， positive control drug， 1 μg/mL）， SCHE-1 and SCHE-2 low-dose and high-dose groups （0.5， 1 mg/mL）. The cell viability of RAW264.7 cells was detected by MTT assay. The levels of IL-1β， IL-6 and TNF-α in RAW264.7 were detected by ELISA. These were used to investigate the effects of SCHE-1 and SCHE-2 on the immunological enhancing activity of RAW264.7 cells. The molecular weight and distribution of SCHE-1 were determined by size exclusion chromatography； the monosaccharide composition of SCHE-1 was determined by HPLC pre-column derivatization. Methylation analysis of SCHE-1 was conducted by NaOH method. RESULTS： Compared with negative control group， the activity of RAW264.7 cells was enhanced significantly in SCHE-1 groups and LPS group， which also significantly increased the levels of IL-1β， IL-6 and TNF-α in cell culture fluids （P＜0.01）. SCHE-1 was an effective component with immunopotentiating activity. The neutral sugar content of SCHE-1 was 40.05％， the uronic acid was 35.62％， and the protein was 8.89％. SCHE-1 was a mixture， molecular weight of which was 62-6 119 Da； monosaccharide was mainly composed of galacturonic acid， arabinose （Ara） and galactose （Gal）. The results of methylation analysis showed that the backbone was composed of 1→3， 1→4 and 1→6 linked Gal， and branches were on the O-6 position of the 1→3 linked Gal， and the non-reducing terminals were Ara. CONCLUSIONS： SCHE-1 may be the effective component of immuno potentiating activity， and main component of SCHE-1 is polysaccharide. SCHE-1 may regulate the immune function by activating macrophages to release IL-1β， IL-6 and TNF-α.