The (Y,Eu)2O3 precursor prepared by microwave with ultrasonic-assisted co-precipitation is superior to the one prepared by co-precipitation of conventional approach as well as co-precipitation assisted by microwave. The effect of preparation conditions on the morphology and particle size of (Y,Eu)2O3 precursor was completely investigated in this study. The ideal conditions were optimized as 0.25M Ln3+ ions concentration, 80°C reaction temperature, 90 minutes reaction time and 0 minute ageing time. Consequently, the (Y,Eu)2O3 precursor in the needle-like shape with average size of 0.25μm in diameter was obtained. The possible mechanism was also presented.