The aim of this work was to study substrate speciflcity and inhibition kinetics of ascorbic acid, 4-hexylresorcinol, L-cysteine and citric acid on PPO obtained from honeysuckle. The results show that the best substrate is chlorogenic acid because of the lowest Km value 0.0059mmol/L; ascorbic acid, 4-hexylresorcinol and L-cysteine demonstrate reversible inhibition, and their IC50 values are 0.062，0.053，0.140mmol/L. Citric acid shows irreversible inhibition to PPO with IC50 value of 0.048mmol/L. Lineweaver-Burk plotting show that ascorbic acid, 4-hexylresorcinol and L-cysteine are mixed type, non competitive and anti competitive inhibitors, with the inhibition constants KI of 1.620, 4.587, 0mmol/L, and KIS of 1.995, 0, 3.780mmol/L, respectively.