A series of Pd/FeOx catalysts were prepared using co-precipitation method via controlling the washing operation after co-precipitation of the catalyst precursors. The prepared catalysts were tested by the hydrogenation reactions of nitrobenzene, benzaldehyde and styrene, respectively. The highest activity could be obtained when the catalyst precursors were washed for ten times containing similar to 2.2 ppm chlorine concentration in the aqueous phase. XPS characterization suggested that a suitable Pd-0/Pd delta+ ratio might be important for the high activity. TEM characterization showed that smaller nano-Pd particles can be generated and TPR characterization suggested the formation of more easily reducible Pd species when the catalyst precursors were washed for 10 times. Less or over-washing of the catalyst precursors result in coagulation of the nano-Pd particles. The washing operation, chlorine concentration, catalyst structure and catalytic performance can be related reasonably. The current results should promote the controllable preparation of active Pd-based catalysts. (C) 2014 Elsevier B.V. All rights reserved.