These results indicate that the TGF-β1 activator can at least partially block the I-125 seed irradiation-induced cell migration inhibition by restoring p-Smad3 protein level and further prove that the I-125 seed irradiation inhibits cell migration of HCC cells by suppressing the TGF-β1/Smad signal. The gene discussed is SMAD3; the disease is hepatocellular carcinoma.