Objective To study the expression,immunological effect and prognosis analysis of G2 and S phase-expressed protein 1(GTSE1)in hepatocellular carcinoma(HCC),and its potential action mechanism.Methods Using the data provided by the public da-tabases The Cancer Genome Atlas(TCGA),the Kaplan-Meier,Tumor Immune Estimation Resource(TIMER)and Gene Expression Profiling Interactive Analysis(GEPIA)databases were used to analyze the gene expression,immunological effect and prognosis of GTSE1,and the expression of GTSE1 in clinical samples was verified by immunohistochemical experiments.Gene Ontology(GO)and Kyoto Ency-clopedia of Genes and Genomes(KEGG)enrichment analysis of GTSE1-related differential genes was performed by R software.Results GTSE1 was significantly overexpressed in human cancer tissues,and was significantly associated with poor prognosis of liver cancer(P＜0.05).GTSE1 gene expression was significantly correlated with the abundance of infiltrating immune cells in HCC(P＜0.001).GTSE1-related differentially expressed genes were mainly enriched in gene modules such as nuclear division,organelle fission and ion channel activity.The signaling pathways involved mainly include neuroactive ligand-receptor interaction and cell cycle.Conclusion GTSE1 expression is significantly up-regulated in HCC and is significantly associated with poor prognosis,and plays an important role in immune cell infiltration,which can be used as a prognostic marker and immunotherapeutic target for HCC.