In order to investigate the anti-tumor effects of knockdown of miR-210 combined with radiotherapy on human hepatoma xenograft in nude mice, SMMC-7721, SMMC/Lv-scr and SMMC/Lv-anti-miR-210 cells were subcutaneously implanted into nude mice, when the diameter of tumor reached 6 mm–8 mm, we assessed expression of miR-210 and relative protein in tumor tissues. After irradiation of 8 Gy X rays under normoxia and hypoxia conditions for 24 h, the cell proliferation and intratumoral microvessel density were detected by Immunohistochemical staining while apoptotic cells in tumer tissue were detected by TUNEL method. The results showed that knockdown of miR-210 decreased expression of miR-210 and hypoxia induced factor 1α (HIF-1α), but increased the expression of proteins which are target genes of miR-210 in hepatoma xenograft. The tumor volums of m210 (Normal+8 Gy) group and m210 (Hypoxia+8 Gy) group were significantly lower than those of scr (Normal+8Gy) group and scr (Hypoxia+8 Gy) group within 9–30 days after the beginning of therapy, respectively. The cell proliferation and intratumoral microvessel density of m210 (Normal+8 Gy) group and m210 (Hypoxia+8 Gy) group were significantly lower than those of scr (Normal+8 Gy) group and scr (Hypoxia+8 Gy) group, respectively, while the percentage of apoptotic cells in tumor tissue was higher 1 day after therapy. These results can be suggested that knockdown of miR-210 combined with radiotherapy can effectively enhance the anti-tumor effects either in normoxia or hypoxia condition on human hepatoma xenograft.Cited