The invention belongs to the field of biomedical macromolecular materials and discloses a non-viral gene transfection vector material based on cationic helical peptide, and a preparation method and application thereof. The structure of the vector material is shown by general formulas (1) to (6) in the description, wherein R1 is C1-6 alkyl, benzyl, methoxypolyethylene glycol, polyethylene glycol or polypropylene oxide, R2 is C1-3 alkyl, benzyl or phenethyl, R3 is methyl or ethyl, R4 is hydroxy, and A is H, C1-3 alkyl, alkoxy, halogen or nitryl; in the general formulas (1) to (4), x represents polymerization degree of polypeptide and is not less than 5; in the general formulas (5) and (6), x represents the ratio of side chain repeating units, with 0<x<1. The cationic helical polypeptide main chain is of Alpha-helical conformation and effectively forms complex micelles with DNA and siRNA, and the material has good transfection efficiency, low cell toxicity and applicable to the transfer of pDNA and siRNA.