Our aim is to test the characteristics and expression activity in brain capillary endothelial cells (BCECs) of DNA-loaded nanoparticles before and after the modification with Antennapedia peptide (Antp). Chitosan (CH), polyethylenimine (PEI) and polyamidoamine (PAMAM) were chosen to prepare the nanoparticles; Lipofectamine 2000 served as control. The incorporation efficiency was determined by agarose gel electrophoresis and PicoGreen assay. Transmission electron microscopy was performed to observe the diameter. The expression efficiency was qualified with fluorescence microscopy and quantified with the luciferase assay system. Heparin and DNase I were employed to investigate the stability. The results indicated that the gene products of DNA/CH nanoparticles and DNA/Lipofectamine 2000 complexes whether modified or unmodified with Antp could not be observed within BCECs. The DNA/PEI nanoparticles and DNA/PAMAM nanoparticles could be internalized into BCECs to a certain extent, and the expression efficiency was enhanced significantly with the modification of Antp. The diameter increased from 100 to 200 nm after modification with Antp. The nanoparticles could protect themselves from the displacement of anionic substances and the digestion of DNase I. These observations demonstrated that Antp, polymer and DNA could form stable nanoparticles, and the modification of Antp can enhance the expression efficiency of DNA-loaded nanoparticles in BCECs.