This study aims to evaluate the safety and efficacy of fecal microbiota transplantation (FMT) in reversing drug resistance to the triple therapy regimen in patients with unresectable hepatocellular carcinoma (HCC). The triple therapy consists of transarterial chemoembolization (TACE), lenvatinib, and Sintilimab. The study is a prospective, single-arm, multicenter clinical trial involving 15 participants with mid-to-late stage HCC that has progressed despite the triple therapy. FMT capsules will be prepared by matching the gut microbiome profiles of healthy donors to those of patients who achieved complete response (CR) with the triple therapy. The primary endpoints include objective response rate (ORR), treatment-related adverse events (AEs). Secondary endpoints will assess overall survival (OS), progression-free survival (PFS), and disease control rate (DCR), changes in gut microbiome, metabolomics, and immune subsets before and after FMT.