High mobility group A2 protein (HMGA2), an architectural factor, is highly expressed in various cancer types including lung cancers. It is a candidate target for cancer therapy. RNAi is an effective gene silencing method with low cost and less time-consuming. It is possible to exploit this technology in therapy. Here, 5 siRNAs targeting Hmga2 gene (HMGA2 siRNA1-5) were designed and synthesized. MTT assay, colony formation assay, transwell assay and flow cytometry were used to evaluate the effects of these siRNAs on lung cancer cell lines (NCI-H446 and A549). Results from cell proliferation, clone formation, migration and apoptosis showed that HMGA2 siRNA1, 3, 5 could affect these aspects for both lung cancer cell lines. Among the five siRNAs, HMGA2 siRNA5 showed the greatest inhibition effects. The inhibition effects of HMGA2 siRNA5 are sequence specific and are not due to the induction of interferon response. Taken together, siRNAs targeting Hmga2 gene are potential candidates for lung cancer gene therapy.