Ti2AlNb-based alloys of two different compositions were deposited using a 5 kW CO2 laser. Optical microscope (OM),scanning electron microscope (SEM),energy-dispersive spectrometer (EDS),X-ray diffraction (XRD) and microhardness testing method,were used to investigate the typical microstructure evolution,phase transformation and the corresponding hardness evolution. Experimental results show that for Ti-20%Al-27%Nb (atomic fraction) (A1),the phase transformation occurrs:B2→B2+O→B2 along the laser deposition direction. While Ti-22%Al-27%Nb (A2) is mainly composed of β(TiNb) dendritic and B2+O in the interdendritic. The primary dendrite trunk spacing changes from 25 μm to 80 μm along the deposition direction. For the two different compositions Ti2AlNb-based alloys,the microhardness variation of A1 alloy along the deposition direction is low→high→low,which agrees well with the corresponding microstructure and phase transformation. The microhardness of A2 alloy distributes uniformly except the local region of the dendritic.