To synthesis the "uniform" and "well-crystallized" alloy nanoparticles, relation between the structure of metal complexes in the aqueous solution and reduction mechanism of these alloy nanoparticles were evaluated. Metal complex conditions in an aqueous solution were expected by the calculation using the critical stability constants. Results of the prediction based on calculation clearly demonstrated that only the [Pd2+(EDTA)] complex was generated independently in the solution with the pH range of 5 to 10. Therefore, conditions of complexes in solution (pH8) were evaluated by Electro Spray Ionization Time of Fright Mass Spectroscopy (ESI-TOF-MS) and also Extended X-ray Absorption Fine Structure (EXAFS). Former results clearly demonstrated that mass number and distribution of detected peaks were almost the same to that of simulated peaks of [Pd2+(EDTA)] derivatives which generated by the ESI methods. EXAFS results also showed that 1 st neighbor of Pd was Nitrogen or Oxygen and 2nd neighbor was carbon, thus EDTA attached to Pd. These results indicated that formation of one specific metal complex in the solution was achieved by obeying to the calculation. By the reduction of these controlled mixed solution, only Pd20Te7 was successfully synthesized, since the formations of metal complexes are restricted to [Pd 2+(EDTA)] and [Te4+(citric acid)], respectively.