A series of precious metals (Pd, Pt, Ru, Rh, and Au) supported on commercial activated carbon (AC) catalysts were prepared and their catalytic performance in the selective hydrogenation of cinnamaldehyde (CAL) were evaluated. Among these catalysts, Pt supported on AC pretreated by 10 % KOH under microwave radiation has the highest catalytic activity and selectivity in the selective hydrogenation of CAL, which provided a selectivity to cinnamyl alcohol of 73.4 % with a conversion of CAL of 62.8 %. The structure and morphology of the AC and the precious metal supported catalysts were characterized by BET, FT-IR, XPS, XRD, and TEM. The catalytic performances of various precious metals as active components were compared. The effects of reaction temperature, hydrogen pressure, and reaction time on the catalytic hydrogenation of CAL were investigated. The by-products were analyzed by GC-MS and their formation mechanism was proposed. This work provides an efficient method of using commercial AC as the support for preparing promising catalysts in the selective hydrogenation of CAL.