Abstract: By adopting the design proposal of modular steam generator, the load factor of the sodium-cooled fast reactor (SFR) could be improved. The state of the plant would be about to change in case of loss of steam generator modules in the daily operation, and the modulatory state of the plant should be given by means of design and research. This research selected a typical pool-type SFR to study the state of the plant with loss of one of its steam generator modules, which included establishment of a model to the main heat transfer system, massive matching calculation on its main thermal parameters, discard of those projects that did not meet the relevant operating limits, analysis of key parameters and determination of the optimum state. This work lays a foundation for the design of the state of SFR with loss of steam generator modules.