An ingot of Nb based in-situ composites (NBISC) was produced by a vacuum self-consuming arc melting furnace. The directionally solidified samples were prepared by an electron beam floating zone melting (EBFZM) furnace with a high temperature gradient, and their microstructural characteristics were analyzed. The results show that the microstructure of as-cast NBISC is composed of primary dendrites of Nb solid solution (Nbss) and the eutectic colonies of Nbss plus (Nb,Ti)3Si/(Nb,Ti)5Si 3. In the EBFZM furnace, with the increase of withdrawing rate, the eutectic microstructure of NBISC is refined. The amount of eutectic colonies layers increases. The sizes of (Nb,Ti)3Si/(Nb,Ti)5Si3 lumps or plates decrease and their amount increases. Their morphology tends to more regular, and the distribution becomes more homogeneous. The directionality becomes intensive and the directionally solidified effects are remarkable.