Astragali Radix-Angelica Sinensis Radix (Qi-Gui herb pair) has long been used as a classic herb pair for tonifying qi and nourishing blood.Polysaccharide is one of its major active ingredients.Two of the Qi-Gui polysaccharides named AAPS-1a and AAPS-3a,significantly inhibited the proliferation of human colon cancer cells HCT116 and human lung carcinoma cells A549,with IC₅₀ of (47.59±1.3) μg/mL,(18.33±2.5) μg/mL for HCT116 cells,and IC₅₀ of (52.12±1.1) μg/mL,(170.21±2.3) μg/mL for A549 cells.Furthermore,AAPS-1a and AAPS-3a induced apoptosis in HCT116 and A549 cells.The apoptotic rate of the HCT116 cells were 31.4%,46.5% respectively and the apoptotic rate of the A549 cells were 19.3% and 33.0% separately.Structural analysis showed that AAPS-1a and AAPS-3a were homogeneous polysaccharides with molecular weights of 7.3×105 and 8.5×104 Da,respectively.Our study found two homogeneous Qi-Gui polysaccharides with significant anti-tumor activity in vitro,which provide experimental basis for clarifying the anti-tumor structure of polysaccharides in Qi-Gui herb pair.