Disclosed is a gelatin-based nanoparticle complex for tumor-targeted delivery of siRNA for specific gene silencing in tumor cells. The gelatin-based nanoparticle complex includes: poly-siRNA chains whose ends are modified with thiol groups; and thiolated gelatin bound to the poly-siRNA chains through disulfide crosslinking and charge interactions. The gelatin-based nanoparticle complex is not degraded in the bloodstream and can be efficiently absorbed into tumor cells without cytotoxicity. The delivered siRNA can effectively silence target gene expression. Also disclosed is a method for preparing the gelatin-based nanoparticle complex.