The reactive behavior on hydrogenation of p-nitroaniline in water catalyzed by supported nickel catalyst was studied. The laboratory test and pilot-plant test were conducted. The effects of reaction temperature, pressure, holding time, p-nitroaniline mass concentration and wastewater recycle on the hydrogenation reaction were investigated. The results showed that the product p-phenylenediamine has high mass fraction, and catalyst and water can be recycled. The optimal reaction parameters are that temperature 110℃, reaction time 2~3 h, pressure 2.0 MPa, stirring speed 800 r/min, dosage of initial catalyst 10% (based on the mass of p-nitroaniline, similarly hereinafter), catalyst loss 0.2% (based on the additive mass of initial catalyst). Under these optimal reaction conditions, the conversion of p-nitroaniline was 100%, and the yield of p-phenylenediamine was over 99.5%. The amount of wastewater discharged after wastewater recycle was small and had no effect on catalytic activity and product quality.