Free amino acids and mineral substance in radix of Polygonum cuspidatum, Polygonum elliptica, and Polygonum sachalinense were analyzed by amino acid autoanalyzer and atomic absorption spectrophotometer. Gross contents of free amino acids in root of P. cuspidatum and P. elliptica are 12.99mg/g and 9.58mg/g respectively. The analysis of inorganic constituents of Polygonum sp. showed that it generally contains copper, iron, manganese, zinc, potassium and potassium salt.