The grain boundary engineering has come into vogue and succeeded in improving properties and service performance of polycrystalline materials.. Towards further innovation in grain boundary engineering, external potential fields have been applied to grain boundary and interfacial engineering as a new approach to materials processing. In this article, an overview of our recent works concerning about the effect of magnetic field on interface related phenomena like sintering, elimination of cavities (rejuvenation), evolution of grain boundary microstructure and grain boundary segregation will be made.