A crucial bottleneck in nonviral vector-mediated gene delivery is poor endosomal escape. Here, we constructed novel gene vectors by coupling the stearyl moiety to the N-terminus of the antimicrobial peptide melittin (stearyl-Mel) and its retro isomer (stearyl-rMel) due to their high membrane-lytic activity. As expected, stearyl-Mel showed obvious increases in endosome-lytic activity and transfection efficiency compared with the reported stearyl-TP10. More gratifyingly, the transfection efficiency of stearyl-rMel was around 10-fold greater than that of stearyl-Mel and almost reached the transfection levels of Lipofectamine 2000 due to the enhanced endosome-lytic activity. Furthermore, the stearyl-rMel/p53 plasmid complex exhibited higher p53 expression and antitumor activity than stearyl-Mel, confirming the fact that stearyl-rMel displayed higher transfection efficiency. Taken together, the combination of the stearyl moiety with retro melittin provides a novel framework for the development of excellent nonviral gene vectors.