A Ti₂AlNb-base alloy was deposited on a TiAl-base alloy by using micro-beam plasma melting deposition. Optical microscope(OM), scanning electron microscope(SEM), energy-dispersive spectrometer(EDS), X-ray diffraction(XRD) and microhardness testing methods were used to investigate the typical microstructure evolution, phase transformation and the corresponding hardness evolution. Experimental results show that micro-beam plasma melting deposition of Ti₂AlNb-base alloy are mainly composed of β、O andα₂ phases. With the increasing of distance form TiAl-base alloy, a series of phase evolutions along the compositional gradient occurred: γ+α₂/γ→β(solid solution)+O→β₂+O+α₂(widmannstatten structure)→β(solid solution)+O. The microhardness of gradient material shows a wave-like distribution. The phase morphological evolution during forming of micro-beam plasma melting deposition gradient materials was explained based on the effect of the various elements on the phase stability in TiAl/ Ti₂AlNb -base alloy combining with the effects of special thermal cycle and heat accumulation in micro-beam plasma melting deposition forming.