Nitrogen-doped graphene (NDGR) with amphiphilic surface was efficiently prepared by introducing nitrogen-containing groups on graphene by cold plasma surface modification. By adjusting plasma gas source, discharge power, discharge time and working pressure, the process was optimized. As-prepared NDGR was characterized by Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy (Raman), organic elemental analysis (OEA), transmission electron microscopy (TEM) and water contact angles (WCA). Platinum nano-catalysts supported by NDGR (Pt/NDGR) were evaluated for selective hydrogenation of cinnamaldehyde and crotonaldehyde in water. The results showed that a nitrogen-doped graphene NDGR(O2-NH3) with the excellent surface properties was obtained by a two-step plasma grafting method, that is, using oxygen (O2) as plasma gas source to activate the graphene surface and then using ammonia (NH3) as plasma gas source to graft nitrogen-containing groups on the surface. Compared with graphene supported Pt catalyst (Pt/GR), Pt/NDGR(O2-NH3) prepared under the optimum conditions (discharge power 140 w, working pressure 200 Pa, discharge time 6 min) showed excellent catalytic performance in the aqueous hydrogenation of cinnamaldehyde (CAL) and crotonaldehyde (CRAL). Under the reaction conditions of 80 oC and 3 MPa, CAL conversion over Pt/NDGR(O2-NH3) reached 98% within 4 h, and the selectivity to unsaturated alcohol cinnamyl alcohol (COL) remained high (about 84%). In aqueous hydrogenation of CRAL, the apparent rate constant kapp over Pt/NDGR(O2-NH3) was 0.53 h-1, much higher than that of Pt/GR (0.37 h-1). The selectivity to CROL also remained high (about 40%) at nearly complete reaction. The high catalytic performance of Pt/NDGR(O2-NH3) was attributed to the enhanced properties of graphene surface after grafting a small number of nitrogen-containing groups on it, including the increased anchoring sites for Pt nano-particles, high adsorption performance to substrates and metal-support interaction.