The purpose of these experiments is to study the effects of flavone from Cirsium japonicum DC (FLCJ) on tumor activity and on the regulation of the immune response in mice with S180 and H22 tumors. Pectolinarin and 5, 7-dihydroxy-6, 4'-dimethoxyflavone are two major components of FLCJ. FLCJ, pectolinarin and 5, 7-dihydroxy-6, 4'-dimethoxyflavone can inhibit the growth of the implanted tumors S180 and H22 and promote cellular and humoral immune responses. FLCJ is stronger than Pectolinarin and 5, 7-dihydroxy-6, 4'-dimethoxyflavone in inhibiting tumors and promoting immune response significantly. Our results indicated that the tumor inhibition of FLCJ had close relation with its regulation of the immune response Furthermore, this tumor inhibition by FLCJ may activate the innate immune system, which would be expected as a potential anti-tumor drug.