Hepatocellular carcinoma (HCC) is a prevalent malignancy worldwide, characterized by high morbidity and mortality rates. Risk factors associated with HCC include cirrhosis, alcohol abuse, metabolic syndrome, hepatitis B virus (HBV) infection, and hepatitis C virus (HCV) infection. Unfortunately, the cure rate of HCC remains low, primarily due to difficulties in early-stage detection. The identification of effective therapeutic targets and novel biomarkers is thus imperative. However, the precise molecular mechanisms underlying HCC development remain elusive. Recent studies have indicated a significant correlation between DNA methylation and cancer development. Notably, bioinformatics analysis of human patient databases has revealed amplification of ASH1L, a histone methyltransferase and a homolog of drosophila ASH1, in tumor tissues. Alterations in ASH1L expression have been implicated in the pathogenesis of various diseases, including prostate cancer, lung cancer, uterine cancer, and leukemia. Its molecular mechanism and cellular functions are undergone extensive studies. Specifically, investigating the role of ASH1L in HCC development represents a promising avenue for understanding the underlying mechanisms. Building upon these backgrounds and considerations, this study aims to elucidate the detrimental effects of ASH1L on the prognosis of HCC patients following liver transplantation, as well as the potential underlying mechanisms. With using various approaches, ASH1L was found to be strongly correlated with HCC. Furthermore, ASH1L shows promise as a potential biomarker for early detection, prognosis prediction, and personalized treatment strategies for HCC.