Based on production cases，discussed the analysis and solution process of electrophoretic flow mark issues. Firstly，the influence factors such as electrophoresis process，part structure，oven machine and so on were explained for the rock panel electrophoretic flow mark issues. Then，the Black Belt Six-Sigma method and ideas were used for specific analysis，and combined with tryout verification，simulation analysis and other methods to determine the scheme of adding drainage holes to parts as a long-term solution. Finally，the requirements for the design of the parts were put forward，and avoiding the narrow cavity structure could effectively prevent the defects of electrophoretic flow marks，effectively solve the problem of  electrophoretic flow marks，and avoid polishing and repairing. The analysis and verification methods adopted indicated important reference value for quality issues in production.