The invention provides a targeting sequence for knocking down or knocking out HPV, further provides a recombinant plasmid for knocking down or knocking out HPV in a targeted manner, further provides ananoparticle preparation for treating HPV infection and further provides a method for preparing poly(beta amino ester) polymer. The targeting sequence aims at nine HVP subtypes and is used to establish targeting knock-down/knock-out plasmid, so that corresponding HVP in infected cells can be effectively knocked down or knocked out. New PBAE prepared by the method can efficiently transfect DNA into target cells and has lower cytotoxicity.