Zirconium molybdate gel has an excellent characteristic to be used as a column matrix material of 99m Tc generators. The preparation conditions of zirconium molybdate gels will directly influence their physico-chemical characteristics and thus generator performances. In this work a series of zirconium molybdate gels were synthesized under different conditions and characterized by ICP, TGA, XRD and SEM Techniques. The effects of different parameters including pH of molybdate solution, Zr:Mo molar ratios, order of reactants addition, washing and granulating of gel on the performance of technetium-99m generators were evaluated. The experiments show that the optimum conditions for synthesis of the gel consist of: pH=4-4.5, Zr:Mo ratio of 1:1, gradual addition of molybdate solution to zirconium oxy chloride solution, no washing and grinding the resulted gel.