Abstract: Objective:To investigate the expression and clinical significance of RNA-binding motif protein Xlinked (RBMX) in hepatocellular carcinoma (HCC), as well as its relationship with tumor immune microenvironment (TIME) by applying tumor-related databases. Methods:The mRNA expression of RBMX in multiple HCC datasets and its relationship with clinical parameters of HCC patients were analyzed by combining GEO database and TCGA database, and the value of RBMX in HCC diagnosis model was evaluated by receiver operating characteristic (ROC) curve. Kaplan-Meier survival curve was utilized to analyze the correlation between RBMX expression level and the survival prognosis of HCC patients. CIBERSORT, ssGSEA, and TIMER databases were applied to assess the correlations between RBMX expression and immune indicators, while TISCH database was applied to assess the enrichment of RBMX in immune cells in different HCC single-cell datasets. Immunohistochemistry (IHC) was utilized to verify the expression of RBMX in 23 pairs of HCC tumor and adjacent tissues, and reverse transcription-quantitative polymerase chain reaction (RT-qPCR) was utilized to determine the expression of RBMX in HCC cell lines. Cell counting kit-8 (CCK-8) assay and EdU staining were used to detect the cell proliferation, and Transwell assay was used to detect the cell migration. Results:Multiple datasets showed that the expression of RBMX was up-regulated in HCC tissues (P＜0.001), and its expression level was positively correlated with clinical grade and lymph node metastasis degree (P＜0.001). RBMX had a significant diagnostic value for HCC (AUC=0.936) and was positively associated with a shorter overall survival time of HCC patients (P< 0.001). High expression of RBMX was closely related to the infiltration of M0 macrophages, Treg cells, and Tprolif-related cells (P＜0.05). The abnormal up-regulation of RBMX in HCC was confirmed by 23 pairs of HCC and adjacent tissues, as well as 5 HCC cell lines, while knockdown of RBMX inhibited the proliferation and migration of HCC cells. Conclusion:RBMX may be an immune-related prognostic biomarker for HCC.