Yttrium iron garnet (YIG) nanopowders were synthesized by sol-gel method using Fe(NO3)3·9H2O, Y(NO3)3·6H2O as raw materials. The influence of heat treatment, the citric acid to metal nitrates molar ratio (CA / MN) and PH value on the synthesized powders were investigated using scanning electron microscopy (SEM), thermal analyses (DTA/TGA) and X-ray diffraction (XRD). YIG powders with average grain size of 80~90nm were synthesized after calcining at 1000°C for 4h.