Liver cancers are characterized by high heterogeneity and complexity, posing significant challenges in early diagnosis and prognosis, which burden patients and healthcare systems. Blood metabolomics, an emerging system biology technology, analyzes small molecular metabolites in the blood to reveal metabolic features of tumors, offering novel insights for the early diagnosis and prognosis evaluation of liver cancers. In recent years, substantial progress has been made in identifying specific blood metabolic biomarkers for liver cancers, including hepatocellular carcinoma, intrahepatic cholangiocarcinoma, and metastatic liver cancer, laying the foundation for more precise personalized treatments. However, current studies face limitations such as small sample sizes, insufficient biomarker validation, and the need for standardization. Large-scale, multi-center studies and integrated multi-omics analyses are urgently required to optimize and validate the application of blood metabolomics. This review summarizes the current state of research on blood metabolomics in liver cancers, focusing on its potential and challenges in early diagnosis and prognosis prediction, aiming to provide insights into precision diagnosis and treatment of liver cancers.