The literatures on toxicity and mechanism of different forms of arsenic in realgar were collected and analyzed. Twenty-eight papers in journals home and abroad were consulted and classified. This paper introduces the toxicity and mechanisms of different forms of arsenic in realgar on the liver

kidneys

bladder

nerves

skin

fetal development and etc. The in vivo toxicity of different arsenic compounds is quite different depending on the exiting forms

inorganic arsenic and organic arsenic. AsⅢ can cause liver cells apoptosis and focal necrosis

AsⅤ

MMAⅤ and DMAⅤ can cause liver cells swelling and spotty inflammation. DMAⅤ is more toxic than MMAⅤ. When prolonged exposure to DMAⅤ and MMAⅤ presents

bladder cancer and skin cancer in animals can caused. MMAⅤ and DMAⅤ metabolites are more toxic than iAsⅢ and iAsV to the genes regulating the neurofilament proteins. In addition

iAsⅢ and MMAⅢ can produce significant toxicity to human hematopoietic stem cells. These reports will provide basis for exploring the relations of different forms of arsenic with toxicity.