To overcome difficulties that hampered widespread application of a specific delivery system in cancer gene therapy and to inhibit the growth of solid liver cancer, we utilized a strain of Bifidobacterium longum as a delivery system to transport an endostatin gene that can inhibit growth of tumor. The B. longum strain with the endostatin gene (B. longum-En) was taken orally by tumor-bearing nude mice through drencher preparation. The results showed that B. longum-En could strongly inhibit the growth of solid liver tumor in nude mice and prolong the survival time of tumor-bearing nude mice. Furthermore, tumor growth was inhibited more efficiently when the B. longum-En treatment included selenium. Enriching the B. longum-En treatment with selenium improves the activity of NK and T cells and stimulates the activity of IL-2 and TNF-alpha in BALB/c mice. These results suggest that B. longum may be a highly specific and efficient vector for transporting anticancer genes in cancer gene therapy.