For the product standardization and generic design of slip ring of traction generator, five types of slip ring insulation structures for AC drive diesel locomotive traction generator were introduced. An optimization scheme for the insulation structure of slip ring was proposed. The results of tests, experiments and finite element analysis showed that the optimized structure could meet the requirements of traction generator with rated voltage less than 1 346 V. The reference was provided for the later design of insulation structure of slip ring with different requirements.