Targeted silencing of heparanase gene by small interfering RNA inhibits invasiveness and metastasis of osteosarcoma cells. The effects of targeted silencing of heparanase gene by small interfering RNA (siRNA) on invasiveness and metastasis of osteosarcoma cells (MG63 cells) were investigated in the present study. Two complementary oligonucleotide strands were synthesized and inserted into pGenesil-1 vector based on the mRNA sequence of heparanase gene. The expression vector containing short hairpin RNA (pGenesil-shRNA) was constructed successfully. MG63 cells were randomly allocated into 3 groups: blank group, empty vector (pGenesil) transfected group and expression vector (pGenesil-shRNA) transfected group. Under the induction of Lipofectamine 2000, the recombinants were transfected into MG63 cells. Heparanase gene expression level was detected by RT-PCR and Western blotting. Cell proliferation was measured by MTT assay. Cell invasiveness and metastasis were examined by cell adhesion and Transwell-ECM assays. HUVECs migration assay was applied for the detection of angiogenesis. As compared with negative controls, the mRNA and protein expression levels of heparanase were down-regulated by 76.1% (P<0.01) and 75.3% (P<0.01) respectively in the pGenesil-shRNA transfected group. Meanwhile, the proliferation, adhesiveness, invasiveness and angiogenesis properties of MG63 cells were all significantly inhibited. It was suggested that targeted silencing of heparanase gene by siRNA could dramatically inhibit the invasiveness and metastasis of osteosarcoma cells.