The catalytic hydrogenation of p-nitrophenol to produce p-aminophenol (PAP) was carried out over the catalyst nickel supported on active carbon (AC). The calcination temperature was one of the most important technical conditions: temperature higher than 450 °C would result in the reduction of NiO to Ni phase by AC and the loss of support. The surface area and nickel dispersion over catalyst decreased obviously after 450 °C calcination temperature because of the loss of support and the Ni phase sintering. Addition of K2O enhanced the alkalinity of the Ni/AC catalyst, and the p-nitrophenol stuff performed rather stronger acidity. Therefore, the level of p-nitrophenol adsorption over Ni/AC catalyst was improved, and the reaction efficiency was enhanced consequently. The p-nitrophenol conversion and PAP selectivity reached 97.7 and 99.3% over Ni–K2O/AC catalyst, respectively. During the process of catalytic hydrogenation, higher PAP selectivity was kept successively. It indicated that no side reactions happened during the catalytic hydrogenation of p-nitrophenol.