The present invention relates to a multi-conjugate of small interfering RNA (siRNA) and a preparing method of the same, more precisely a multi-conjugate of siRNA prepared by direct binding of double stranded sense/antisense siRNA monomers or indirect covalent bonding mediated by a cross-linking agent or a polymer, and a preparing method of the same. The preparing method of a siRNA multi-conjugate of the present invention is characterized by simple and efficient reaction and thereby the prepared siRNA multi-conjugate of the present invention has high molecular weight multiple times the conventional siRNA, so that it has high negative charge density, suggesting that it has excellent ionic interaction with a cationic gene carrier and high gene delivery efficiency.