Abstract: The use of low enriched uranium (LEU) fuel is an important trend in the development of space nuclear power in recent years. Based on this, the Monte Carlo program MCNP was used to calculate and analysis the neutronic characteristics of the representative space capable cryogenic thermal engine (SCCTE) core scheme for LEU nuclear thermal rocket (NTR) reactor. The calculation results show that this scheme is a thermal-neutron reactor, and the initial excess reactivity and shutdown depth meet the requirements of normal operation. After optimization of fuel zonal enrichment, the change of radial power is relatively gentle, and the axial power peak moves up further, which is beneficial to increase the hydrogen outlet temperature, thereby increasing the specific impulse. The temperature power effects of fuel, moderator and reflector are all negative values, which meet the design requirements. The hydrogen entry effect is positive, which can compensate for part of the temperature power effect. After entering the water, the effective multiplication coefficient reaches 1.194, which means the current scheme lacks measures for criticality safety as occurring launch accident. This still needs to be further improved.