Finding a safe and efficient gene delivery vector is a major international challenge facing the development of gene therapy. Tannic acid (TA) is a natural cross-linker owing to its hydroxyl and carboxyl groups that can interact with biopolymers for different biomaterial design. In this work, three polyethyleneimine-modified TA polymers were prepared, and the polymers were characterized by FTIR, UV-vis, elemental analysis and 1H NMR. The potential of PTAs as gene vector was studied in vitro, including DNA loading capacity, DNA protection ability and biocompatibility. In addition, the particle size, zeta potential, DNA encapsulation efficiency, cell uptake and transfection efficiency of the PTA-pDNA polyplexes were also studied. The results showed that PTA2k and PTA30k could completely condense DNA at N/P of 2, and PTA600 could only completely condense DNA at N/P of 50. The PTA/pDNA polyplexes could protect DNA from degrading by DNA enzymes and could be efficiently uptaked by cells. Biocompatibility assay showed that PTA had no significant cytotoxicity and effect on cell proliferation compared to PEI. At low N/P ratios of 1-4, PTA showed higher transfection efficiency than PEI, and the transfection efficiency increased with the increase of PEI molecular weight in PTA. At N/P of 3, PTA30k showed the highest transfection efficiency of 23.8%, while PEI30k showed only 6.7%. These results indicate that PTA is a promising candidate vector for safe and efficient gene delivery.