In　this　study,　we　fabricated　poly　(methyl　methacrylate)　(PMMA)　microcellular　foams　featuring　tunable　cellular　structures　and　porosity,　through　adjusting　the　supercritical　CO2　foaming　conditions.　Experimental　testing　and　finite　element　model　(FEM)　simulations　were　conducted　to　systematically　elucidate　the　influence　of　the　foaming　parameters　and　structure　on　compressive　properties　of　the　foam.　The　correlation　between　the　cellular　structure　and　mechanical　properties　was　acquired　by　separating　the　effects　of　the　cell　size　and　foam　porosity.　It　was　found　that　cell　size　reduction　contributes　to　improved　mechanical　properties,　which　can　be　attributed　to　the　dispersion　of　stress　and　decreasing　stress　concentration.