The aim of this study is to deeply search the performance of the coupling system comprised of a direct carbon fuel cell and an alkali metal thermal electric converter. The main contents of this study are to propose the model of the novel coupling system by considering the main irreversible losses, derive the efficiency and power output of the whole system, discuss the influences of the electric current of the fuel cell, the electrolyte thickness, and the ratio of the electrode areas of two subsystems on the systemic performances, and, evaluate and compare the performances of the whole system and the fuel cell. The main novelties are to provide parametric optimum choice criteria and give the reasonably matching schemes of two subsystems. The results obtained reveal the advantages of the present coupling system.