Agglomeration of Y-PSZ and its related properties were studied. The ultrafine $ZrO_2$ powder containg 3 mol% $Y_2O_3$ was prepared by 1) coprecipitation method b) hot petroleum drying method c) sol-gel method and the characteristics of calcined powders and the microstructures of sintered body were observed. Powder prepared by the coprecipitation method was about 125$AA$ in crystallite size and 0.1~1.0${mu}{ extrm}{m}$ of intra-agglomerate pore size when calcined at $600^{circ}C$ for 1 hour. because of small crystallite size and weak agglo merate strength resultant densification of sintered body was high. But above the temperature of 130$0^{circ}C$ efflorescent phenomena due to anions attached to powder surface was observed. Powder prepared by hot petroleum drying method was 65$AA$ in crystallite size and 1~10${mu}{ extrm}{m}$ of intraagglome-rate pore size and it was observed that the agglemerates were formed during the calcining process. In this case despite of small crystallite size the rate of sintering was slow and the existing lenticular interagglomerate pore was not eliminated to the final stage of sintering. Powder prepared by sol-gel method showed solid agglomertes due to rapi dhydrolysis reaction. In this powder which involves strong solid agglomerates overall sintering rate was determined by the sintering between the agglomerates and therefore sinterability of powders made by sol-gel method was very poor.