Yttrium Aluminum Garnet (YAG) has become a favorite solid laser basis material for its significant optical, mechanical and thermal properties. It′s the key point to synthesize YAG nano-particles with well-crystallized, uniform grain, good dispersion for perfect transparent ceramic. Loosely dispersed YAG nano-particles and pure cubic crystal phase are synthesized by co-precipitation-freeze drying method，using higher purity A1(NO3)3·9H2O, Y(NO3)3·6H2O and NH4HCO3 as raw materials. The YAG nano-particles are characterized by DSC/TG, X-Ray diffractometer (XRD), scanning electron microscope (SEM) and laser granulometer, etc. After calcined at 1200 ℃, the well-crystallized YAG nano-particles are obtained with higher purity, weak agglomeration, uniform grain size and regular shape.