Abstract: The aim of the study was to optimize the formulation of L,L-ethyl cysteinate dimer (ECD) kit by uniform design.In the experimental design,the pH of A vial and the SnCl₂ content of B vial were selected as the independent variables,and the radiochemical purity of the ^99m Tc complex was selected as the dependent variables.Response surface method was utilized for the selection of optimal formulation.The results showed that the relationship between dependent and independent variables was best fitted to the regression equation: y=0.567+0.103x₁+9.68e^-4x₂-9.86e^-4x₁³-5.48e^-8x₂³. In the best formulation predicted,the pH of A vial was 6 and the SnCl₂ content of B vial was 65μg.The predicted values were close to the experimental values.The optimized formulation showed higher radiochemical purity compared with the marketed kit.Therefore, uniform design is applicable for the formulation optimization of ECD kit.