Objective To detect the expression of mitochondrial dynamics proteins (Mfn2 and Drp1) in thyroid squa?mous carcinoma cell line SW579 and the effects of Mitochondrial division inhibitor, Mdivi-1, on proliferation, apoptosis and invasion of SW579. Methods In SW579 and Nthy-ori 3-1 cell lines, the expression levels of Mfn2 and Drp1 were deter?mined by western blot while the transcription level of Mfn2 and Drp1 mRNA were measured by RT-PCR. Then, SW579 cells were divided into control group (DMSO, 0.1%) and Mdivi-1 low, medium and high dose groups (Mdivi-1 of 15,30 and 45μmol/L were incubated with cells for 16 hours respectively). Then the ability of cell proliferation was detected using MTT assay, the mitochondrial membrane potential was determined by fluorescence spectrophotometer, the expression levels of cy?tochrome C and Caspase-3 were quantified by Western blot and the transcription level of the Cyt C and Caspase-3 mRNA were determined by RT-PCR. The ability of invasion in each group was measured with Transwell assays. Results Com?pared with Nthy-ori 3-1, the mRNA transcription and protein expression levels of the Mfn2 was remarkably decreased, while the mRNA transcription and protein expression of the Drp1 was significantly increased in SW579 cells (P<0.01). Compared with control group, the cell survival rates and mitochondrial membrane potential of SW579 were decreased dramat?ically (P<0.01). The mRNA transcription and protein expression of the cytochrome C and Caspase-3 were increased dra?matically (P<0.01) and the capability of invasion was markedly decreased in all the Mdivi-1 groups in a dosage dependent manner compared with those in control groups (P<0.01). Conclusion Abnormal mitochondrial dynamics may be involved in thyroid squamous cell carcinoma SW579 cells;Mdivi-1 can inhibit the cell proliferation and invasion as well as induce apoptosis.