Haematitum is in use in Korean medicine. The Korean medical doctors use Haematitum for calming the liver and suppressing yang(平肝 潛陽), etc. We investigated toxicity, poisoning symptoms, poisoning treatment and prevention against poisoning of Haematitum. The results were summarized as follows: 1.The main ingredients of poisoning are ferric oxide, etc. The ingredients of poisoning from Haematitum mainly cause stimulating symptoms on digestive system, nervous system, cardiovascular system, and urinary system, etc. 2.In order to prevent against poisoning of Haematitum, the patients should keep usage, dosage and notes.