In this study, we explored the relationship between the PAX8-PPARγ expression changes and malignant biological behavior of thyroid tumors from in vivo and ex vivo experiments, respectively, and the results showed that PAX8-PPARγ promoted the proliferation and antiapoptotic ability of thyroid cancer cells, and PAX8-PPARγ expression inhibition affected the tumorigenic ability of nude mice in vivo. The gene discussed is PPARG; the disease is thyroid tumor.