The present invention provides a double-stranded RNA structure, which comprises a polymer compound covalently bonded to a double-helix oligo RNA useful for the treatment of diseases, particularly cancer, in order to enhance the delivery of the double-helix oligo RNA, and further comprises a target-specific ligand bonded thereto, a preparation method thereof, and a technique of delivering the double-helix oligo RNA in a target-specific manner using the RNA structure. A nanoparticle composed of the ligand-bonded double-helix oligo RNA structures can efficiently deliver the double-helix oligo RNA to a target, and thus can exhibit the activity of the double-helix oligo RNA even when the double-helix oligo RNA is administered at a relatively low concentration. Also, it can prevent the non-specific delivery of the double-helix oligo RNA into other organs and cells. Accordingly, the ligand-bonded double-stranded RNA structure can be used for the treatment for various diseases, particularly cancer, and can also be effectively used as a new type of double-helix oligo RNA delivery system. Particularly, the ligand-bonded double-stranded RNA structure can be effectively used for the treatment of diseases, including cancer and infectious diseases. Moreover, the present invention relates to a hybrid conjugate, which comprises a hydrophilic material and hydrophobic material bonded to both ends of an antisense oligonucleotide (ASO) by a covalent bond in order to enhance the in vivo stability of the ASO, a method for preparing the hybrid conjugate, and a nanoparticle composed of the conjugates. The ASO-polymer conjugate according to the invention can increase the in vivo stability of the ASO, making it possible to efficiently deliver the therapeutic ASO into cells. Also, the ASO-polymer conjugate can exhibit the activity of the ASO even when it is administered at a relatively low concentration.