Liquid phase separation phenomenon has been paid widespread attention on developing in-situ amorphous matrix composites.In this study, firstly, we determined the isothermal section of the phase diagrams at 1273, 1373 and 1473 K in the Cu-Ni-Nb ternary system.Thermodynamic assessment of the Cu-Ni-Nb system was also carried out based on experimental data of activity and phase equilibria using the CALPHAD (Calculation of Phase Diagrams) method.The calculated result of vertical section shows a stable liquid miscibility gap (L1+L2) (Fig.1).Secondly, based on this liquid miscibility gap, a new crystalline/amorphous composite with a droplet-type microstructure is fabricated in Cu-Ni-Nb immiscible system by using melt-spinning method.It is found that the Cux(Ni38Nb62)100-x (x=0,10, 20, 30 at.％) alloys undergo liquid-liquid phase separation in the undercooled liquid state,and then solidified into Cu-rich crystalline phase and NiNb-based amorphous phase (see Fig.2).The fcc Cu-fich crystalline droplets are dispersed in the NiN-b-based amorphous matrix.