A preparation method for a water extract of the fruiting body of Antrodia camphorata (ACW) is provided. The method includes steps of: (a) providing the fruiting body and (b) boiling the fruiting body in water to obtain the water extract. This polysaccharide-rich water extract from A. camphorata induces the maturation of dendritic cells, enhances T cell proliferation and INF-γ production, and polarizes them toward the Th1 pathway. ACW can be effectively applied in cancer immunotherapy.
