Beta-tricalcium phosphate (beta-TCP) powder doped with metal (Na(+) or Mg(2+)) ions was prepared using a novel polymerized complex method that involves a reaction between metal ions and an organophosphorus chelating agent [(2-phosphonobutane-1.2.4-tricarboxylic acid (PBTA)]. The precursors were uniformly gelled by the chelation and dehydration condensation of the carboxyl groups and phosphonic acid groups in PBTA, and metal (Ca(2+), Na(+), and Mg(2+)) ions. When precursors with/without Na(+) ions were used, the beta-TCP phase crystallized through the alpha-TCP phase, whereas when precursors containing Mg(2+) ions were used, it crystallized directly. The crystallization temperature of the beta-TCP phase from the precursors decreased with the addition of Na(+) and Mg(2+) ions. The lattice constants of each sample after heating the precursors at 1000 degrees C were almost the same as those of beta-TCP powder doped with metal ions via a solid-state reaction. The synthesized samples also had a stoichiometric composition. Heating the precursors above 550 degrees C resulted in a unique chain structure, which remained unchanged even after the addition of Na(+) and Mg(2+) ions. However, at the same heating temperature, the particle size of the samples increased with the addition of Na(+) ions, but decreased with the addition of Mg(2+) ions.