Propylene glycol (PG) wastewater seriously threatens aquatic lives and causes health damage to human beings. Several early studies for PG degradation focused on biological process, which usually proceeds at a slow rate and is often inhibited by substances which are toxic to the microorganisms. In this paper, Fenton method was exploited for treating PG wastewater in a semi-continuous reactor with adding ferrous sulfate (FeSO4) and hydrogen peroxide (H2O2) to the reactor, respectively. Semi-continuous applications of H2O2 and Fe2+ could result in low steady state of HO*, which would minimize HO center dot scavenging and further increase PG oxidation efficiency. Under the optimal conditions, 99.1% of PG conversion and 88.4% of COD removal were achieved. In addition, pseudo-first-order model, in which the concentration of HO center dot was assumed to remain constant, was established. The intrinsic activation energy of HO* with PG, calculated by Arrhenius-equation was 35.18 kJ/mol. The intrinsic reaction rate constant of HO center dot with PG around optimal conditions was 1.56-1.72 x 10(8) M-1 s(-1). After Fenton's reaction, PG molecules could not be thoroughly oxidized to H2O and CO2. Intermediates, such as aldehyde, acetone, methanol, formic acid, and acetic acid, were checked by GC-MS, which all had a very low content and toxicity. As a homogeneous catalytic oxidation, Fenton oxidation is a feasible treatment for PG wastewater for its low toxicity, low price, and high efficiency. (C) 2011 Elsevier B.V. All rights reserved.