A series of catalysts with different acid strengths were obtained by constructing unsaturated pentacoordinate (Al³⁺_penta) sites in Al₂O₃ and loading with boron. The effects of support properties and the addition of boron on the strength and type of catalyst acid were investigated, and their influence on the dehydrogenation performance of methylcyclohexane (MCH) was discussed. In Pt-B/Al₂O₃-600 catalysts containing Al³⁺_penta sites, the strongly acidic L acid sites gradually decreased and the weakly acidic [L + B] acid sites gradually increased with increasing boron loading, indicating coverage of the Al³⁺_penta site by boron. In Pt-B/Al₂O₃-750 catalysts without Al³⁺_penta sites, strongly acidic L acid sites gradually decrease with increasing boron loading and weakly acidic [L + B] acid sites remains essentially unchanged. For Pt-B/Al₂O₃-600 catalysts, the effect of boron on the interaction of Pt with Al₂O₃ is minimized when the loading of boron is between 0 and 1 wt% and the MCH dehydrogenation performance increases with the number of weak acid sites. At a boron loading of 1 wt%, the abundance of weak acid sites maintains the dispersion of Pt and allows a suitable interaction between Pt and Al₂O₃, thus enhancing the dehydrogenation performance of MCH.