Heparanase participates in the growth and invasion of human U-2OS osteosarcoma cells and its close relationship with hypoxia-inducible factor-1α in osteosarcoma. Although the expression of heparanase is associated with invasion and metastasis of various human cancers, the effects of heparanase on human osteosarcoma have not been evaluated. We showed that down-regulating the expression of heparanase significantly reduced proliferation and invasion of human U-2OS osteosarcoma cells. Furthermore, heparanase silencing by short-hairpin RNA (shRNA) was associated with decreased hypoxia-inducible factor-1α (HIF-1α) level, implying that heparanase was associated with the expression of HIF-1α. This result was confirmed by immunohistochemistry analysis. In osteosarcoma tissues, immunohistochemical results revealed that heparanase expression had a close correlation with that of HIF-1α and they had a strong relation with presence of pulmonary metastasis (P<0.05).Heparanase-positive samples had higher microvessel density (MVD) than heparanase-negative samples. Similarly, compared with HIF-1α-negative samples, HIF-1α-positive samples had higher MVD. Therefore, heparanase and HIF-1α facilitated tumor angiogenesis and promoted pulmonary metastasis of osteosarcoma.