Siliceous　mesocellular　foam　(MCF)　with　tunable　cell　and　window　size　was　synthesized　by　the　acid　catalyzed　sol-gel　reaction　of　tetraethoxysilane　in　the　presence　of　triblock　copolymer　Pluronic　P123　(EO20PO70EO20)　as　structure-directing　agent.　The　cell＇s　size　of　MCF　is　increased　with　the　increase　of　1,3,5-trimethylbenzene　amount,　while　the　window＇s　size　of　MCF　could　be　tailored　between　4　and　18.2　nm　without　affecting　the　cells　size　by　adding　of　NH4F.　The　obtained　MCF　materials　were　employed　as　carriers　for　catalase　immobilization.　FT-IR　spectra　and　N-2　sorption　show　that　the　catalase　is　immobilized　into　the　mesopores　of　MCF.　MCF　with　window　size　of　12.9　nm　shows　high　catalase　loading　and　activity,　suggesting　that　matching　the　window＇s　size　with　enzyme　molecular　diameter　is　a　critical　factor　in　attaining　efficient　immobilization　since　smaller　window　size　prevents　larger　enzyme　from　entering　the　pore　and　larger　window　size　causes　the　leakage　of　enzyme.　The　thermal　and　storage　stabilities　of　the　immobilized　catalase　were　also　improved　due　to　the　shield　of　the　mesopores　of　MCF.