ObjectiveTo synthesize a new type of cationic polymers (β-amino esters)(PBAE) and to study its role as a gene vector. MethodsPBAE was synthesized by the Michael addition reaction. PBAE/pDNA complex nanoparticles were prepared by self-assembly, and the gene tranfection efficiency mediated by the nanoparticles into HEK293 cells in vitro was observed. ResultsWhen weight ratio of PBAE/pDNA was 501, pDNA was completely wrapped. And the transfection efficiency of PBAE/pDNA nanoparticles (PBAE/pDNA weight ratio being 2001) was significantly higher than PEI/pDNA nanoparticles(43.3%±3.7% vs 30.3%±2.1%, P<0.05). ConclusionCationic poly(β-amino esters) can electrostatically bind to and condense anionic DNA into nanometersized particles. PBAE/pDNA nanoparticles has a high transfection efficiency in in vitro transfection experiments.