Abstract: Background　Hypopharyngeal squamous cell carcinoma (HSCC) is one of the most aggressive malignancies among head and neck squamous cell carcinomas with the poorest prognosis. Its immunosuppressive tumor microenvironment is closely associated with CD8 ⁺ T cell exhaustion; however, the underlying regulatory mechanisms remain poorly understood. Objective　To identify T cell-specific subpopulations in HSCC through single-cell RNA sequencing (scRNA-seq), screen for key molecules associated with CD8⁺ T cell exhaustion, and validate their functional roles.Methods　Tumor tissues and paired adjacent normal tissues were collected from five patients with HSCC for scRNA-seq. Cell subpopulations were identified by unsupervised clustering, and differential expression analysis was performed on exhausted CD8⁺ T cells to screen candidate genes. Survival and correlation analyses were conducted using the TCGA database. In vitro, CD8⁺ T cells were isolated from the peripheral blood of healthy volunteers by magnetic bead sorting, and a T cell exhaustion model was established through sustained CD3/CD28 stimulation. Following lentivirus-mediated FUT8 silencing, exhaustion phenotype and proliferative changes were assessed by flow cytometry, qRT-PCR, and CCK-8 assays. A co-culture system with the HSCC cell line FaDu was established to evaluate cytotoxic effects.Results　A total of nine major cell clusters and multiple T cell subpopulations were identified. Exhausted CD8⁺ T cells were significantly enriched in tumor tissues and highly expressed PDCD1, LAG3, and TOX. Differential expression analysis revealed that FUT8 was significantly upregulated in tumor-derived exhausted CD8⁺ T cells. High FUT8 expression was significantly associated with reduced overall survival (P = 0.005) and positively correlated with multiple exhaustion markers. In vitro experiments confirmed that FUT8 silencing reduced PD-1 and LAG-3 expression, upregulated IFN-γ, TNF-α, and IL-2 levels, and partially improved the proliferative status of exhausted cells. In co-culture assays, FUT8-silenced exhausted CD8⁺ T cells exhibited significantly enhanced cytotoxicity against FaDu cells.Conclusion　FUT8 is a specifically upregulated gene in exhausted CD8⁺ T cells in hypopharyngeal carcinoma. It may be associated with the maintenance of the exhausted CD8⁺ T-cell phenotype and antitumor immune alterations, and may represent a potential candidate target for HSCC immunotherapy.