Platinum/montmorillonite nanocomposites were first prepared in supercritical methanol and characterized by means of FTIR, TEM, XRD and EDS. Pt particles were uniformly distributed in montmorillonite host with fine particle size, mainly with diameter in the range from 4 to 8 nm. The catalytic performances of the resulting Platinum/montmorillonite nanocomposites were then examined, and it was found that they displayed both high selectivity and conversion in the hydrogenation of nitrobenzene to aniline.