The invention relates to a method for preparing a 3-arylbenzofuran ketone compounds. The method comprises that: phenolic compounds and phenylacetic-acid structure compounds are subjected to alkylation in a mol ratio of 1:1-2 at a temperature between 60 and 270 DEG C; an alkylation catalyst is an acidized crosslinked montmorillonite catalyst prepared by acidizing, loading, crosslinking and activating montmorillonite; the weight ratio of phenolic compounds serving as reaction raw material to the montmorillonite alkylation catalyst is 1:0.01-0.2; an esterification catalyst is added; the mol ratio of the phenolic compounds serving as the reaction raw material to the esterification catalyst is 1:0.001-0.02; esterification is performed at a temperature between 60 and 170 DEG C; supported metal ions of the acidized crosslinked montmorillonite catalyst are 1 to 10 mmol/g of montmorillonite; and the mol ratio of silicon to aluminum is 2-10:1. The 3-arylbenzofuran ketone compound prepared is suitable for serving as organic polymer sensitive to oxidation and heat/light-induced degradation, particularly a polyolefin stabilizer.