Though low-temperature sintering of MgB2 superconductors below Mg melting point can effectively depress volatility of Mg and increase sintering density, its development was limited in recent years for the reason that it usually took very long time to form complete MgB2 phase with excellent J(c) at low temperature. In present work, significantly improved J(c) was surprisingly obtained in the MgB2 samples sintered at 575 degrees C for only 5 h after short-time ball milling, even though formation of MgB2 phase is not completed and lots of residual Mg is still present in these samples. The grain connectivity in prepared samples is obviously improved compared to referred MgB2 sample sintered at high temperature, which is responsible for the improvement of J(c). The method developed in present work seems bring a new opportunity for the development of low-cost practical MgB2 superconductors with improved J(c) without using expensive nanometer-size dopants or high-temperature sintering. (C) 2013 Elsevier B.V. All rights reserved.