The miR let-7b-5p (a kind of microRNAs) has many pathophysiological regulation effects, including human hepatocellular carcinoma (HCC) pathogenesis. This study investigated whether nanoparticle-mediated miR let-7b-5p could jointly enhance the therapeutic effect of sorafenib on HCC by inhibiting the proliferation of HCC cells, inducing apoptosis, and reversing drug resistance. We evaluated the level of miR let-7b-5p in sorafenib-resistant HepG2 cells (HepG2R) and HepG2 HCC cells by qRT-PCR and analyzed the biological effects of hepatocellular carcinoma treated with sorafenib with miR let-7b-5p, and further studied the toxicity of nanoparticles (Ab-miR-NPs) that deliver miR let-7b-5p mimics and target GPC3 on the surface of hepatocellular carcinoma cells. Results showed that, in HepG2 cells, the expression level of miR let-7b-5p was significantly higher than that in HepG2R cells. Targeted nanoparticle Ab-miR-NPs mediated the delivery of miR let-7b-5p to the HCC cytoplasm and released miRNA after being broken down, down-regulating the expression of IGF1R and inhibiting AKT/mTOR and Ras/Raf signal transmission. Ab-miR-NPs not only enhanced the proliferation of sorafenib in cultured HepG2R cells and induced cell apoptosis efficiency, but they also improved the anti-tumor activity in the mouse models. These results indicated that GPC3 antibody-modified PLGA-PLL (polylactic acid-glycolic acetic copolymer grafted hyper-branched polylysine) loaded miR let-7b-5p polymer nanoparticles combined with sorafenib may be a new treatment strategy for HCC resistant to sorafenib.