The catalytic properties of phosphotungstic acids for the Friede1Crafts acylation of 2methoxynaphthalene(MN) with aceticanhydride (AA) were investigated．The effect of various reaction conditions, such as reaction temperature, ratio of reactants, reaction time and catalyst dosage on conversion of 2methoxynaphthalene and the selectivity to main product were studied. The results show that 2methoxy1acetonaphthone was main priority products in the acylation reaction of 2methoxynaphthalene. The optimal reaction conditions were as follows: 0.08 g H3PW12O40 as catalyst, reaction time 3 h, reaction temperature 100 ℃, molar ratio of 2methoxynaphthalene to acetic anhydride 1∶2. Under these conditions, the conversion of 2methoxynaphthalene is 83.32%and the selectivity is up to 91.39% .