The cell structure and performance of microcellular polymethylvinylsiloxane (PMVS)/carbon nanotubes (CNT) foam prepared by supercritical CO2 (scCO(2)) were investigated. The results showed that the uniformly dispersed CNT significantly reinforced the PMVS matrix because of the strong interaction between molecular chain and CNT. In addition, the onset thermal decomposition temperature of the nanocomposite was increased by 60 degrees C with the incorporation of CNT (0.5 wt%) compared with that of PMVS matrix. Furthermore, as a kind of heterogeneous nucleating agent, CNT could effectively decrease the nucleation energy barrier, resulting in the uniform cell morphology of PMVS/CNT foam with smaller cell size and higher cell density.