The rhizomes of sweet flag (Rhizoma Acori calami) is the remedy that people of many countries in the world widely used in medicine. However, the mineral component in the rhizomes of sweet flag and medicine from the rhizome has not been fully investigated. Here we use the research material is dried rhizomes of sweet flags which have been harvested in Ho Chi Minh city and bought at the drugstore to study the mineralogy cadmium, lead, copper and zinc (Cd, Pb, Cu, Zn) in these medicinal plants. The results showed that the average content of cadmium is 0.028 mg/kg, lead is 0.184 mg/kg, copper is 3.29 mg/kg, Zinc is 28.5 mg/kg. Concentration of Cd, Pb, Cu, Zn in dried medicinal plants and in decoction do not exceed allowable concentration.