The　isobutane/butene　(I/O)　ratio　in　the　pore　is　a　crucial　factor　for　enhancing　the　catalytic　stability　of　zeolitic　catalysts　in　C4　alkylation　process.　In　this　work,　the　influence　mechanism　of　the　Si/Al　ratio　on　the　I/O　ratio　in　the　pore　for　H-BEA　zeolite　was　investigated　via　CB-GCMC　methods　under　realistic　alkylation　conditions.　It　is　found　that　the　I/O　ratio　in　the　pore　decreases　dramatically　with　decreasing　the　Si/Al　ratio　due　to　the　higher　adsorption　heats　of　1-butene　over　the　acid　sites　than　that　of　isobutane.　Therefore,　there　will　be　an　optimal　Si/Al　ratio　for　C4　alkylation,　which　is　in　good　agreement　with　the　experimental　results.　Furthermore,　the　relationship　between　the　I/O　ratio　in　the　pore　and　feedstock　over　the　H-BEA　zeolite　with　different　Si/Al　ratios　was　built.　We　found　that　increasing　the　I/O　ratio　in　the　pore　by　improving　the　I/O　ratio　in　the　feedstock　is　limited,　when　the　Si/Al　ratio　is　much　low.　The　external　surface　modification　of　catalyst　will　be　an　effective　method　to　improve　the　I/O　ratio　in　the　pore.　These　results　are　of　great　significance　to　the　rational　design　of　high-efficiency　C4　alkylation　catalysts.