Abstract: Objective To investigate the effect of tivozanib, a novel tyrosine kinase inhibitor, on the proliferation of thyroid cancer cell line SW579 and vascular endothelial cell line HUVEC in vitro and the related mechanisms. Methods SW579 and HUVEC were exposed to tivozanib at different concentration (1, 2, 4, 8 and 16 μM) for 72 h, and tivozanib-untreated cells were taken as control. The effects of tivozanib on cell proliferation were assessed by CCK-8 cell viability assay, cell imaging analysis and immunofluorescent staining of mitosis cells. Cell cycle analysis was performed by flow cytometry. Results Cell viability assay indicated that tivozanib inhibited the proliferation of both SW579 and HUVEC(P<0.05), in a time- and dosedependent manner, with median IC50 of 4 and 8 μM, respectively. Cell imaging analysis showed that tivozanib at IC50 significantly decreased cell densities of SW579 and HUVEC (P<0.05). Immunofluorescent staining of mitosis cells demonstrated that mitotic indexes of tivozanib-treated SW579 and HUVEC were decreased significantly (P<0.05). Flow cytometry demonstrated that tivozanib arrested SW579 and HUVEC at G1 and G2/M phases, respectively(P<0.05). Conclusion Tivozanib significantly inhibits the proliferation of SW579 and HUVEC by inducing cell cycle arrest at different phases. Tivozanib is indicated as a novel tyrosine kinase inhibitor for the treatment of thyroid cancer by targeting tumor cells and vascular endothelial cells.