Abstract: The pellet bed reactor (PeBR) featured with high-power density, compact reactor design and full retention of fission products, has promising application prospect for the space nuclear power system. In this paper, a steady-state thermal-hydraulic analysis code was developed for the space nuclear electric propulsion (NEP) type PeBR. The thermal-hydraulic design features and safety performance were analyzed during full power operation. The optimization focused on the porosity in the hot and cold frits to eliminate hot spots in the core. The results show that the peak temperature of fuel pellets has a large safety margin, as high as 873 K. The cold frit porosity has little effect on the coolant flow distribution. Adopting hot frit with porosity ratio of 2.0 could eliminate hot spots in the core. In addition, the pressure loss across the core could be reduced when increasing the inlet coolant pressure. The results in this paper could provide valuable suggestion and guidance for the design and safety analysis of the NEP type PeBR.