Accumulative evidence has confirmed that, miR-17-92, a typical polycistronic mRNA cluster, was up-regulated in various solid tumors, and play an important role in the occurrence and development progress of tumors. In our study, we detected the six members of miR-17-92 cluster in osteosarcoma cell line, finding that the expression of miR-17 and miR-19b was up-regulated significantly. Further studies have found that Mfn1 was one of the target genes of miR-19b and the transcription and expression level of Mfn1 were down-regulated by miR-19b. MTS, flow cytometry, TUNEL-DAPI, Annexin V-FITC and transwell assay demonstrated that Mfn1 significantly blocked the cell cycle, promoted apoptosis and inhibited proliferation and invasion of osteosarcoma cells. Whereas, miR-19b targets 3'UTR sequences of Mfn1 genes inhibit the expression of Mfn1, thus inhibited Mfn1 triggered anti-cancer effect. Taken together, miR-19b functions by targeting Mfn1 reduce the protein expression level, thus provides a novel target to understand the molecular biology and genetics mechanisms of occurrence and development of osteosarcoma, contributing to the diagnosis and therapy of osteosarcoma.