Abstract: Phellinus igniarius is a kind of rare officinal fungi. The paper aims to study the effect of compound P. igniarius oral liquid’s polysaccharide on mouse’s immunity function. From mouse carbon clearance test, macrophage phagocytosis of chicken red blood cells (semi in vivo method), organ and body weight ratio, natural killer (NK) cell activity in mouse (determination of lactate dehydrogenase assay) were studied in four aspects. The results showed that high dose (40 mL/kg) of the compound P. igniarius oral liquid could obviously enhance the ability of carbon clearance in mouse; middle (20 mL/kg) and high dose treatments could significantly enhance the phagocytosis of chicken red blood cells of mouse macrophage phagocytic percentage and phagocytic index; low (10 mL/kg), middle and high dose treatments could significantly enhance the NK cell activity in mouse. These shows that compound P. igniarius oral liquid has enhanced mononuclear macrophage function, the activity of NK cell function. In conclusion, compound P. igniarius oral liquid’s polysaccharide could enhance immune function, can significantly improve the specificity and non-specificity immune function.