Arsenic is a kind of traditional Chinese medicine. According to the “Compendium of Materia Medica”, arsenic is very poisonous. The toxicity of arsenic is well known to the world, and is one of the 36 types of toxic Chinese medicines under strict control in China. Because of this, “arsenic can cure leukemia and liver cancer” has raised too many questions from the public. In fact, as early as in ancient times, there are records of the application of arsenic drugs such as arsenic to treat malignant diseases, including tumors, and in 1972, Harbin Medical University was the first to discover the efficacy of arsenic acid (i.e. arsenic trioxide), the main component of arsenic, in acute promyelocytic leukemia from a Chinese medical prescription. Hepatocellular carcinoma is a malignant tumor that occurs in the liver and is usually in the middle to late stage when detected. Surgical treatment remains the treatment option of choice. Post-surgical treatment options are limited. Although chemotherapy is an important tool for postoperative treatment of other tumors, there has been a lack of effective chemotherapy regimens in hepatocellular carcinoma. After a long study, researchers were surprised to find that arsenic has a good therapeutic effect on liver cancer. Arsenic also has the effect of killing tumor stem cells. Tumor stem cells, thought to be the root cause of tumor growth and drug resistance. Traditional chemotherapeutic drugs, often have no effect on tumor stem cells that are in G0 stage. In contrast, arsenic can not only act on common tumor cells, but also act on tumor stem cells at the same time, inducing apoptosis of both cells, and has basically no effect on normal cells, with little side effects and low price, which is one of the few drugs found to act on tumor stem cells. In view of the significant therapeutic effect of arsenic trioxide in liver cancer, the Chinese Drug Administration approved the use of arsenic trioxide as a single drug in the treatment of liver cancer in 2004. 2011, arsenic trioxide was included in the systematic use of the Ministry of Health’s “Standard for the Treatment of Primary Liver Cancer”. Arsenic trioxide has been widely used clinically in the treatment of primary liver cancer and has achieved good clinical efficacy. Currently, targeted therapy sorafenib is recommended internationally as the main drug for liver cancer treatment. Our clinical phase II observation of 111 patients with towel advanced primary liver cancer receiving arsenious acid injection monotherapy resulted in the achievement of therapeutic effects equal to those of sorafenib. Sorafenib is expensive and unaffordable to the general public, and it is much cheaper if treated with arsenic acid. The side effects are minimal.