The syntheses of intermetallic compounds through liquids reactions between two components are studied. Two different behavious to form the intermetallic compounds in the reaction are observed. One is a catastropic reaction which leads to a-rapid formation of intermetallic compounds and the other is a non-catastropic reaction which results to slow formation. The Mg-Bi and Mg-Sb system were selected to monitor the catastropic reaction and the Al-Sb system was chosen for the non-catastropic reaction. The reason of the reaction speed was rationalized by the heat evolution and the mixing enthalpies. Temperature for the Mg-Bi and Mg-Sb system was raised by about 250∼350℃ during intermetallic formations and the interface layer between the two liquids was planar and thick. But in the case of the Al-Sb system, temperature rise was only 4∼5℃ and many perforate and thin interfaces were observed. A new method to synthesize and separate the intermetallic compounds from the reacted liquids has also been developed. It is separated by density differences in a salt bath. The new method has been proved to attain the intermetallics without contamination from the base metals and can be applied not only to the Mg-Bi and Mg-Sb system which are catastropic reaction systems, but also the Al-Sb system which has slow reaction kinetics.