An organometallic composition containing an organometallic compound (I) containing Ag, an organometallic compound (II) containing Au, Pd, or Ru, and an organometallic compound (III) containing Ti, Ta, Cr, Mo, Ru, Ni, Pd, Cu, Au, or Al, wherein the metal components of organometallic compounds (II) and (III), respectively, are present in an amount of 0.01˜10 mol % based on the amount of Ag in the organometallic compound (I), and a method of forming a metal alloy pattern using the same. Silver alloy patterns can be obtained through a simplified manufacturing process, which patterns have enhanced heat resistance, adhesiveness and chemical stability. The method may be applied to making a reflective film for LCD and metal wiring (gate, source, drain electrode) for flexible displays or flat panel displays, and further to CMP-free damascene processing and PR-free ITO film deposition.