Polyphenol oxidase(PPO) was purified from an extract of Puerariae Radix by ammonium sulfate fractionation followed by Sephadex G-150 column chromatography, which resulted in a 56-fold increase in specific activity. The enzyme was optimum of pH 6.5. The optimum temperature of enzymic reaction was about $40^{circ}$. The enzyme was thermostable with a half-life equal to 32 min at $70^{circ}$. Km values of the PPO for catechol and pyrogallol from Lineweaver Burk plots were $1.3{ imes}10^{-2}M$, $1.16{ imes}10^{-2}M$, respectively. The substrate specificity of the Puerariae Radix PPO showed high affinity toward pyrogallol. Reducing reagents such as cysteine, potassium metabisulfite, ascorbic acid, 2-mercaptoethanol completely inhibited the PPO activity at $10^{-2}M$ level. Linewear-Burk analysis of inhibition data revealed that the inhibition by cysteine, 2-mercaptoethanol, 4-nitrocatechol, potassium cyanide was competitive with Ki values of $4.3{ imes10^{-2}M,;0.73{ imes}10^{-6}M,;6.9{ imes}10^{-6}M,;6.4{ imes}10^{-7}M$, respectively. The browning reaction by PPO was observed to decrease temporarily with the addition of sodium diethyl dithiocarbamate, a well known copper chelating agent. Among the divalent cations, $Cu^{2+}$ ion was strong activator on PPO and $Mn^{2+},;Co^{2+}$ ions was effect on PPO activity. $Zn^{2+},;Mg^{2+}$ ions was inhibitor on PPO.