A series of emulsion catalysts were successfully synthesized with quarternary ammonium cations and heteropolyanions, and they were characterized by TG/DTA, FTIR, 31P MAS NMR and EPR. The emulsion catalyst with intact Keggin-structure, [C 18H 37N(CH 3) 3]H 2[PW 12O 40] (PW 12), is inactive for benzothiophene (BT) oxidation with H 2O 2 as oxidant under atmospheric pressure at 30 °C. Moreover, the metal-substituted catalysts PW 11M (M = Ti, Mn, Fe, Co, Ni and Cu) show rather low activity with the conversion less than 15% for BT oxidation. Whereas, the catalyst with mono-lacunary Keggin-structures, [C 18H 37N(CH 3) 3] 5Na 2[PW 11O 39] (PW 11), could completely catalytic oxidize BT into the corresponding sulfone under the same conditions. After careful characterizations of the catalysts, it is found that only PW 11 catalyst could effectively transform into the active polyperoxometalates species in the presence of hydrogen peroxide in non-polar solvent.