Liver cancer is a leading cause of cancer death, making it as the second most common cause for death from cancer globally. Though many studies before have explored a lot for liver cancer prevention and treatment, there are still a lot far from to know based on the molecular mechanisms. Janus kinase 2 (JAK2) has been reported to play an essential role in the progression of apoptosis, autophagy and proliferation for cells. Therefore, we were aimed to investigate the underlying mechanisms by which JAK2 performed its role in ameliorating liver cancer. JAK2 knockout liver cancer cell lines were involved for our experiments in vitro and in vivo. Western blotting, quantitative RT-PCR (qRT-PCR), ELISA, Immunohistochemistry, and flow-cytometric analysis were used to determine the key signaling pathway regulated by JAK2 for liver cancer progression. Data here indicated that JAK2, indeed, expressed highly in cancer cell lines compared to the normal liver cells. And apoptosis and autophagy were found in JAK2 knockout liver cancer cells through activating Caspase-3, Cyclin-D1 and mTOR regulated by STAT3/5 and PI3K/AKT signaling pathway. And also, the liver cancer cells proliferation was inhibited. In addition, tumor size and weight were reduced by knockout of JAK2 in vivo experiments. These findings demonstrated that JAK2 and its down-streaming signaling pathways play a direct role in the progression of liver cancer possibly. To our knowledge, it was the first time to evaluate the role of JAK2 knockout in improving liver cancer from apoptosis, autophagy and proliferation, which could be a potential target for future therapeutic approach clinically.