Aiming at achieving fine and directionally-solidified microstructure of Nb-Si based alloy,Nb,Si and Ti powder particles were utilized as the raw materials,and laser melting deposition (LMD) experiments were conducted with 1500 W and 2000 W laser power,respectively.The microstructure characteristic,micro-hardness,and indentation fracture toughness were examined by scanning electron microscope (SEM),X-ray energy dispersive spectrometer(XEDS) and X-ray diffraction (XRD).The results showed that the two kinds of as-deposited Nb-175i-23Ti alloy samples were mainly composed of Nbss,(Nb,Ti)3Si and Ti-rich Nbss,and the microstructure presents rapid directionally-solidified characteristic,in which the crystallographic direction of Nbss and crys-tallographic direction of (Nb,Ti)3Si tend to be parallel to the LMD building direction.With the laser power increasing from 1500 W to 2000 W,the microstructure became more oriented and homogeneous.For the sample at 2000 W,the dendrite spacing was only about 1-2 μm,and Nbss and (Nb,Ti)3Si couples grow alternately and they are parallel to the building direction strictly.In the meantime the micro-hardness and indentation fracture toughness reached 1075 HV and 20.3 MPa·m1/2,respectively,indicating significant improvement by the direc-tional growth of fine Nbss and (Nb,Ti)3Si phases,and the dimple fracture mode of the Nbss dendrites.