Poly(amido-amine) (PAMAM), one of the most widely studied dendrimers in the field of drug and gene delivery, can enhance the stability of DNA and deliver it to cell cytosol; hyaluronic acid (HA), a simple disaccharide unit, can polymerize and is considered a polymer of non-immunogenicity, which has an intrinsic targeting property for many cancer cells by interacting with CD 44. In this study, we had synthesized and characterized a series of PAMAM modified by HA. and PAMAM was conjugated by HA with different grafting density (5%, 15%, 25%) and molecular weight (HA3850, HA17200). We had investigated the particle size, zeta potential and Agarose gel electrophoresis assays of polyplexes. Besides, the cytotoxicity, transfection efficiency and the mechanisms of transfection of new polyplexes were assessed following transfection in Hela, Bel-7402 and HepG2 cells lines. In the results, modified by HA, the cytotoxicity of polymer had reduced and the size of some polymers also below 200 nm in appropriate weight ratio, and transfection efficiency had also close to the polyplexes G4 PAMAM/DNA were observed. Compared with the unmodified dendrimers compounds, the DNA delivering capacity of PAMAM G4-HA3850-5% and PAMAM G5-HA3850-5% had improved in cancer cells line. It is a potential candidate used for targeted gene delivery.