4-tert-butyl-2- (α-methylbenzyl) phenol（t-BAMBP）was synthesized from tert-butylphenol and styrene catalyzed by concentrated phosphoric acid. The optimal synthesis conditions were as follows: a reaction temperature of 150 ℃, a reaction time of 150 min, a reactant ratio of 1∶1.8, and a catalyst dosage equal to 1.5% of the feed stock. Under such conditions, the conversion percent of tert-butyl phenol was 81.29%, and the yield of t-BAMBP was 81.04%. The synthetic products were separated and purified by vacuum distillation. The proper distillation temperature was 156~157 ℃, and the absolute pressure was 400Pa. The purity of t-BAMBP was higher than 98.79%. The tert-butyl group removing mechanism in the t-BAMBP synthesis process was analyzed, and the by-products forming routes were deduced.