Abstract: Transparent polycrystalline yttrium aluminum garnet (Y₃Al₅O₁₂),for its predominant optical,mechanical and chemical properties,is becoming a new generation of solid-state laser matrix material.The homogeneously dispersed,less agglomerated and superfine nanometer precursor powders are greatly favorable to fabricate highly transparent laser ceramics.The black powders are synthesized by using citrate-gel combustion method with Y₂O_3,Al(NO₃)₃·9H₂O and citric acid as raw materials,and the ytterium aluminum garnet (YAG) precursor powder with a size less than50nm is manufactured by calcining the black powders at temperature1100℃.The YAG precursor powders are characterized by means of XRD,FT-IR and TEM and the grain sizes are calculated by the Scherrer's formula.It is exhibited that the forming temperature of YAG crystal phase is between 850~900℃,the pseudo-YAG crystalline appears during the calcination and then transforms to pure YAG at temperature 1050℃,the grain sizes linearly ascend with the calcination temperature increasing,the particle size observed under TEM is conformable to that calculated by Scherrer's formula.