Abstract: Precursors of yttria were prepared in aqueous solution with yttrium nitrate as raw material,ammonia,ammonium carbonate,and ammonium tartrate as precipitators,and with polyethylene glycol,sodium dodecyl benzene sulfonate,and cetyltrimethyl ammonium bromide as surfactants.Then yttria powder was prepared by calcining precursor in the air.XRD,SEM,and IR were applied to characterize the samples and laser grain size analyzer was used to analyze the crystal aggregation degree of the samples.Results indicated that cubic phase yttria powder with one-level crystal diameter of 13 nm,40 nm,and 63 nm all were obtained by calcining the prepared precursors with ammonia,ammonium carbonate,and ammonium tartrate as precipitators respectively for 2 h at the temperature of 673 K.The particle size of aggregate of yttria precursor (yttrium hydroxide) which has been treated by small molecule organic-alcohol back-flowing was 58.8 nm and the particle size of yttria aggregate after calcination was 423 nm.Therefore,it was proved that organic-alcohol back-flowing treatment has prevented the aggregation of particles.