Without addition of any thermodynamically stable perovskite compound such as PbTiO3, Pb(Mg1/3Nb2/3)O3 was fabricated by a new sol-gel route, and the processing parameter was studied. The result showed that the chelating effect of ammonium citrate was relatively better than that of citric acid in this system. When the ratio of ammonium citrate to Nb2O5 was 8.33, the colloid of Nb2O5·nH2O was in state of transparency. The effects of heat treatment on the formation of perovskite phase of Pb(Mg1/3Nb2/3)O3 powders were characterized by X-Ray Diffraction (XRD) method. With increasing heat treatment temperature or holding time, pyrochlore phase turned into perovskite phase gradually, and after second calcination, the content of perovskite phase increased significantly from 54% to 72%.