Oximes were oxidized to the corresponding carbonyl compounds in good to high yields by environmentally friendly and green oxidant,H_2O_2 catalyzed by montmorillonite K-10 supported cobalt(Ⅱ) chloride. Oximes were oxidized to the carbonyl compound in good to high yields by environmentally friendly and green oxidant, H 2 O 2 catalyzed by montmorillonite K-10 supported cobalt (Ⅱ) chloride.