Abstract: According to the problem of merging unit during the test on electrical fast transient/burst（EFT/B）,the characteristics of the EFT/B are analyzed and the anti-interference methods for solving the EFT/B problem of the merging unit are proposed.The improved filter structure with metalized polyester film capacitors and transient voltage suppressor（TVS）is proposed to enhance high-frequency interference suppression.The wiring and layout of the mother PCB is optimized to reduce the impact of coupling between different circuits.The results of the test show that the improved merging unit is able to meet the requirements of EFT/B of grade 4.