TiCp/Al　prefabricating　alloy　was　fabricated　by　in　situ　reaction,　and　its　microstructure　and　mechanical　properties　were　investigated　by　means　of　XRD,　SEM,　EDAX,　DTA　etc.　It　is　found　that　the　melting　point　of　Al　matrix　in　TiCp/Al　prefabricating　alloy　is　about　635°C,　which　is　lower　than　that　of　pure　Al,　but　there　exists　a　kind　of　stronger　combinational　force　between　TiC　particles,　which　makes　the　TiCp/Al　prefabricating　alloy　keep　its　shape　at　high　temperature　of　800°C.　The　TiCp/Al　prefabricating　alloy　is　melted　in　molten　Mg　with　different　technologies.　The　results　show　that　the　TiCp/Al　prefabricating　alloy　will　not　be　melted　after　holding　for　60　min　at　800°C　without　mechanical　stirring;　on　the　other　hand,　by　means　of　mechanical　stirring　it　can　be　melted　in　molten　Mg,　and　therefore　makes　TiC　distribute　uniformly　in　molten　Mg.　The　melting　mechanism　of　the　TiCp/Al　prefabricating　alloy　in　molten　Mg　can　be　explained　as　follows:　with　the　help　of　shear　force　of　molten　alloy　flow　produced　by　mechanical　stirring,　the　combinational　force　between　TiC　particles　will　be　destroyed,　and　therefore,　the　particles　can　easily　distribute　uniformly　into　the　molten　Mg.