The role of the gut microbiome in the development and progression of liver cancer has long been recognized. However, the presence of microbes in tumors that were previously considered sterile has only recently been discovered. The intratumor microbiome in liver cancer likely originates from various sources, including the gut, hematogenous spread from other mucosal locations, adjacent non-cancerous tissues, and co-metastasis with the tumor cells. As a newly discovered component of the tumor microenvironment, it regulates host immune responses, promotes chronic inflammation, modulates metabolic pathways, and exerts other influences in liver cancer. These unique features offer potential new biomarkers for liver cancer prognosis and treatment response. Exploring the complex interactions between intratumor microbiome and the host to modulate or target the intratumor microbiome may provide new avenues for liver cancer treatment. This article provides a comprehensive review of our current understanding regarding the potential origins of the intratumor microbiome in liver cancer, its unique characteristics, and the underlying mechanisms by which it affects liver cancer. Furthermore, we discuss the promising clinical implications and potential challenges that remain before this knowledge can be fully integrated into clinical practice.