Taking Nb and Si elemental powders as raw materials,dense Nb/Nb5Si3 composites were successfully fabricated by a spark plasma sintering(SPS)technology.The microstructural features of the synthesized composites were analyzed by OM,SEM,XRD and EPMA.The formation mechanism of the composites was also investigated by a quenching test.The results show that the prepared composites consist of Nb and Nb5Si3 phases,and Nb particles uniformly distribute in the in-situ synthesized Nb5Si3 matrix.During the SPS process,an interfacial reaction occurs between Nb and Si particles to synthesize Nb5Si3 until reactant silicon has been completely reacted.