Abstract: Abstract：Ozonized sunflower oil (Oleozon) is an oxidizing agent with excellent stability. In order to evaluate its application prospect on root-knot nematodes, investigations on the use of series of Oleozon were conducted. In vitro studies were carried out to determine the efficacy of Oleozon on mortality of second-stage juveniles and egg hatching against root-knot nematode. Additionally, the control efficiency of Oleozon with different ratios on muskmelon root-knot nematode was tested via pot experiments. The results indicated that Oleozon was effective against the nematode in regards to mortality of second-stage juveniles and egg hatching inhibition and better than ozonized water and phoxim. Compared with ozonized water, the mortality rate of juvenile was higher in Oleozon at 0.5 g/L. When the dosage of Oleozon above 2 g/L, the control efficacy in juvenile mortality was even more significantly than 1000 times liquid of 50% phoxim. Besides, the reduction for the egg mass population of nematodes was dosage dependent. As is evident from the data, the egg hatching in ootheca was reduced more than 60% when the concentration of Oleozon above 5 g/L, while the values of phoxim was only 28.9%. Different concentrations of Oleozon caused 51.1～96.8% suppression in egg hatching of dissociative nematode, with 33.1% and 57.4% in controls. Oleozon at 5 and 10 g/L showed highest efficiency to nematodes in in vivo pot experiments with 79.2% and 88.7% than controls, which were 18.9% and 50.9%, respectively. Furthermore, Oleozon prominently decreased the quantities, second-stage juveniles and eggs of root-knots compared with the control treatments. Results suggest that application of Oleozon gave better growth on muskmelons.Thus, Oleozon showed good bio-control potential against root-knot nematodes in muskmelon protection.