It is well known that no single phase Pb( Mg 1 3 Nb 2 3 ) O 3 could be prepared by the conventional ceramic route due to the formation of pyrochlore. A new thermal shock method has been developed for the synthesis of the stoichiometric ultra-fine powder ( ø=70–250nm) of Pb( Mg 1 3 Nb 2 3 ) O 3 from metal-citrate gel. The optimum synthetic temperature and reaction temperature have been determined as approximately 900°C and 40 minutes, respectively.