Abstract: Due to the imbalance of multiple specialshaped cavities in the family mould, there are some defects such as short shot and delaying effect easily caused during the injection molding process.This results in a poor quality of the formed products.Based on the melt flow analysis, the section radius and length of the runner were determined as two important factors affecting the volume flow and pressure distribution of the melt.Considering of the complex mold structures for indication lamp post, the maximum difference of filling pressures at the end of filling process among different subrunner was taken as an unbalance factor, and an integrated rapid optimum mechanism with a multivariate structure variety was constructed according to the uniform design method.The optimal runner scheme was obtained by combining with the global optimization of the genetic algorithm.The numerical simulation results indicated that the runner system with improved structure parameters has a better balance filling effect than that with the initial ones.