Abstract: Excitation system is an important component of synchronous generator, and it is also the guarantee for the stability of the whole system. In order to avoid equipment damage and system instability caused by unexpected shutdown or insufficient protection, many aspects need coordination between generatortransformer protection and excitation system, which is an important part of generation-transmission coordination.Taking a 650 MW nuclear power unit as an example, a brief analysis is carried out on the setting calculation and verification coordination of parameters related to excitation limit and generator-transformer protection. The results demonstrate that the settings of the excitation system and the generator-transformer group of the unit are reasonable, both of which do well in cooperation, and keep a certain time difference to ensure that the limit function of the excitation system is prior to the protection action of the generator-transformer group and meet the requirements of generation-transmission coordination.