The microstructure and properties of Nb/Nb5Si3 in situ composites prepared from Nb-20Si, Nb-20Si-5Ti, Nb-20Si-15Ti and Nb-20Si-24Ti by the spark plasma sintering (SPS) technique. The microstructures of the synthesized composites were analyzed by SEM, XRD and electron probe microscopy (EPMA). The effects of Ti addition on the microstructure and properties of Nb/Nb5Si3 in situ composites were studied. The result show that the main phase of the composites changes from Nb/Nb5Si3 to Nb/(Nb, Ti)5Si3 due to the Ti addition. The pure Ti phase and Nb3Si phase are found in the composites when the Ti content reaches to 24%. With the content of Ti increasing, the hardness of Nb/Nb5Si3 in-situ composites would be decreased, but the high temperature oxidation property would be increased