Novel Keggin heteropolyacid anion based Bronsted acidic ionic salts [SO3H(CH2)(4)Mim](n)H3-nPMo12O40 (n = 1, 2, 3) were synthesized and used as catalysts in the nitration of aromatic compound in HNO3 (67%). The catalytic activity was in the order of [(CH2)(4)SO(3)HMim](3)PMo12O40 > [(CH2)(4)SO(3)HMim](2)HPMo12O40 > [(CH2)(4)SO(3)HMim]H2PMo12O40. The effect of catalyst loading, quantity of nitro acid and temperature on nitration of toluene was discussed, and 87.7% yield and good para selectivity with 1.19 ratio of ortho to para can be obtained with optimized catalyst [(CH2)(4)SO(3)HMim](3)PMo12O40. The catalyst can be easily separated from the products and recycled for three times without significant loss of activity.