【Abstract】 Objective To investigate the effects of TNF-a on the EMT in PTC cell line BCPAP, confirmed wether the AKT-TWIST1 pathway was involved in these progressions. Methods The expression levels of proteins of EMT makers E-cadherin, N-cadherin and Vimentin, AKT, TWSIT1 were analyzed using Western blot. The expression level of mRNA of TWIST1 was analyzed using RT-PCR. The effect of TNF-« on cell migration and invasion after AKT inhibiting by HY-89 was assessed by Wound-healing and Trans well assay. Results After the involvement of TNF-a, the protein expression of E-cadherin of BCPAP decreased, while the protein expressions of N-cadherin and Vimentin increased (P<0.05). The mRNA of TWIST1 increased (P<0.05) , and the protein expressions of AKT and TWIST1 increased (P<0.05). After AKT inhibitors were applied, TWIST1 protein expression was decreased and cell invasive and metastasis capacity was decreased. Conclusion Our results showed that TNF-a could induce EMT to promote the invasive and metastasis capacity of human papillary thyroid carcinoma cell line BCPAP through the ATK-TWIST1 signaling pathway.