The invention relates to a cross-linking polymerization acidic ionic liquid alkylating catalyst. The catalyst is obtained through the steps that a 4-halogenated-1-vinyl pyrazole monomer, 1-vinyl-3-alkyl imidazole bromide and crosslinkers crosslinkers are subjected to copolymerization to obtain cross-linking polymer ionic liquid, the cross-linking polymer ionic liquid reacts with halohydrocarbon toobtain substituted cross-linking polymer ionic liquid, and finally the substituted cross-linking polymer ionic liquid and organic acid are subjected to ion exchange to obtain the catalyst, wherein the general molecular formula is defined in the description, R1 is -CH2(CH2)2CH3 or -CH2(CH2)4CH3, R2 is -CH2(CH2)mCH3, m is 0, 2, 4 and 6, X is one of Cl, Br and I, Y<-> is SO3CF3<-> or CF3COO<->, thepolymerization degree is 2-50, a polymer b is 2-50, a polymer c is 2-50, and a polymer d is 2-50. Serving as a novel environmentally-friendly solid acid heterogenous catalyst for an alkylation reaction, the catalyst has the excellent catalytic performance, the catalytic efficiency can be effectively improved, and when styrene and o-xylene are catalyzed to generate the alkylation reaction, the yield of a diphenylethane product is larger than 90%.