Thermal analysis, phase identification and microstructure observation were adopted to explore the accelerating sintering effect of Cu-doping on the low-temperature formation of MgB2 below Mg melting. It is found that the Cu-doping sintering of MgB2 bulk followed an activated sintering mechanism and thus obviously promoted the reaction between Mg and B forming bulk MgB2. Accordingly, dense MgB2 bulks with excellent T-c and J(c) were successfully synthesized by the Cu-doping sintering at 575 degrees C for only 5 h. Further, a sintering model was proposed to illuminate the Cu-doping activated sintering mechanism. It is found that during the Cu-doping activated sintering process, the local Mg-Cu liquid generates firstly and then segregates to the interface between Mg and B particles, which can wet Mg particles and provide a rapid transport for the diffusion of neighboring Mg atoms into B particles resulting in the accelerated formation of MgB2 phase. (C) 2008 Elsevier Ltd. All rights reserved.