DNA polymerase iota (polt) is a member of low-fidelity Y-family of DNA polymerases. Our previous studies have demonstrated that the overexpression of polt is associated with the poorer prognosis in lung cancer patients. Here, we designed the small interfering RNA (siRNA) targeting polt gene (POLI) to investigate the effect of poll on the proliferation, apoptosis, and invasion of the lung cancer cell line A549 in order to reveal the role of polt in lung cancer progression. Our results showed that siRNA of POLI had no significant effect on the proliferation and apoptosis of the lung cancer cell line A549. However, siRNA of POLI could inhibit the migration and invasion of the lung cancer cell line A549 by upregulating the E-cadherin expression and downregulating the expressions of N-cadherin, MMP2, and MMP9. Together, our findings indicate that polt plays a positive role in lung cancer progression via promoting the migration and invasion of lung cancer cells. Therefore, polt might be a potential target for the clinical treatment of lung cancer in the future.