To chemically bond polymer and organoclay, low molecular weight trimethoxysilyl-modified polybutadiene (Silane) was used in this study. When Silane was added, ethylene-vinyl acetate copolymer (EVA)/ethylene-1-butene copolymer (EtBC)/methyl tallow bis-2-hydroxyethyl quaternary ammonium-modified montmorillonite (OHMMT)/Silane foams with and without maleic anhydride grafted EtBC (EtBC-g-MAH) display lower compression set than EVA/EtBC foams. According to the compression set result, OH-MMT is more effective in improvement of compression set than dimethyl dihydrogenated tallow quaternary ammonium-modified montmorillonite (DM-MMT) because in addition of OH groups in the organoclay surface, the OH groups of the alkylammonium ion existed in interlayer of OH-MMT may react with silanol group of Silane. The possible chemical reactions between Silanol groups of Silane and the hydroxyl groups of OH-MMT and DM-MMT were proved by ATR-FTIR experiments.