Abstract: This paper deals with the thermodynamics and kinetics of the reaction of B₂O₃ with Mg-Li alloy for the production of MgO particulates reinforced Mg-Li composites, which were examined with DTA and water quenching. It can be seen that the reaction of B₂O₃ with Mg-Li alloy could take place at the usual melting temperature of Mg-Li alloys and the reaction rate is quick. Fine, spherical and dispersed MgO particulates were formed by reactive synthesis process, and the presence of MgO was verified by XRD data. The mechanism of reaction is also discussed.