Preparation of nanosized (Y,Gd)2O3:Eu powders by co-precipitation processing is reported. Phase transformation during calcination was studied by means of DTA-TG FT-IR, SEM and XRD in detail. It was found that the morphologies and X-ray excited luminescence of (Y,Gd)2O3:Eu powders were greatly influenced by the precipitants used. The (Y,Gd)2O3:Eu powder resulted from the complex precipitants of NH3•H2O and NH4HCO3 possessed best microstructural features with grain size of about 30nm and specific surface area of 38m2/g after being calcined at 8500C for 2hr, showing a much finer grain and less agglomeration than those from other two precipitation processing. It was demonstrated that nanosized (Y,Gd)2O3:Eu powder from complex precipitant exhibited much higher luminescence intensity at 611nm under excitation of X-ray (70Kev). which might be attributed to less degree of agglomeration among primary grains, decreasing the probability of non-radiation relaxation.