In　this　paper,　we　establish　a　novel　sintering　protocol　for　ex　situ　MgB2　bulk　in　an　open　system　by　using　Mg　vapor.　The　Mg　vapor　successfully　restrains　both　the　continues　oxidation　and　decomposition　of　MgB2,　even　after　96　h　at　900　degrees　C.　Such　robust　protection　given　to　the　ex　situ　MgB2　bulk　at　high　temperature　provides　the　possibility　of　improving　the　superconducting　connectivity　and　critical　current　density　(J(c))　using　long-term　sintering　at　high　temperatures.　The　effect　of　sintering　time　on　phase　formation,　microstructure,　superconducting　properties,　and　the　mechanical　properties　of　ex　situ　MgB2　bulk　are　systematically　investigated.　A　comparison　of　our　novel　protocol　and　the　most　successful　ex　situ　MgB2　bulk　sintering　process-the　powder-inclosed-tube　method　(PICT)-is　also　discussed.　Our　novel　protocol　can　improve　superconducting　properties　to　the　same　level　as　with　the　PICT　method　but　allows　MgB2　bulk　to　be　used　in　an　open　system.　This　makes　dealing　with　ex　situ　MgB2　bulk　for　engineering　applications　feasible.