A noble-metal-free reduced graphene oxide composite, copper nanoparticles (Cu NPs) loaded reduced graphene oxide (Cu/RGO), was prepared via a one-step in-situ reduction method. Furthermore, the catalytic activity of the composite for reduction of 4-nitrophenol (4-NP) was investigated. The results showed that the composite was a highly efficient, stable and low-cost catalyst for transformation of 4-NP. In the composite, Cu NPs acted as the cocatalyst and the RGO acted as the substance of electron transfer. The catalytic mechanism was also suggested. Copper nanoparticles loaded reduced graphene oxide (Cu/RGO) was prepared via a one-step in-situ reduction method. The Cu/RGO composite exhibited high catalytic activity and good recycle stability for treatment and transformation of 4-nitrophenol. Compared with the similar catalysts, the Cu/RGO composite is a cheaper, stable and highly efficient in practical application.