Abstract: Oxidation of 4-terpineol with 30% H2O2 catalyzed by quaternary ammonium peroxotungsto-phosphate catalystπ-C5H5(CH2)11CH33PW4O32 in 1,2-dichloroethane gave p-menthane-1,2,4-triol. The product was easily separated as a white crystalline powder by filtration and structurally identified by means of EA, IR, 1H NMR and 13C NMR. Under the optimal reaction conditions, i.e. 4-terpineol 12.3 mmol, 1,2-dichloroethane 5 mL, molar ratio of hydrogen peroxide to 4-terpineol 1.25:1, mass percentage of catalyst to 4-terpineol 2.98%, reaction temperature 50 ℃, reaction time 1.5 h, the conversion rate of 4-terpineol and yield of p-menthane-1,2,4-triol were 99.8% and 58.0%, respectively. The purity of product can reach more than 98%. The preliminary herbicidal assay had that p-menthane-1,2,4-triol had an obvious post-emergence inhibitory effect against shoot growth and root elongation of barnyard grass (Echinochloa crusgalli L.). The percentage inhibition of root growth and shoot elongation at 10 mmol/L concentration in herbicidal test were 100% and 81.4%, respectively.