Abstract: We report the discovery, development and prospective applications of the new superconductor MgB2. Both from theoretical and experimental studies, it has been found that the superconductivity in MgB2 is induced by electron phonon coupling and can be described by the BCS theory with S－wave pairing symmetry. However, two energy gaps have been observed to appear at the same temperature in MgB2, which Sheds new light to the study of superconductivity and calls for more work. On the application side, the most obvious application is to make superconducting magnets using MgB2 wires ( tapes ). This magnet can work at 20K with a closed－circle refrigerator and produce a magnetic field of 4T.