Abstract: Heat pipe cooled space reactor is an important candidate for space reactor power system. The materials applied in space reactor core are quite different to those in PWR core. Taking HP-SMTCs reactor core as an example, materials containing rhenium, molybdenum, lithium and beryllium are widely used. In order to examine the influence of evaluated nuclear data of these isotopes to the nuclear design of heat pipe cooled space reactor, Monte Carlo criticality calculations were done using cross section data from various sources and versions for HP-SMTCs core in different configurations. Neutron data files from ENDF/B series, JEFF and CENDL for rhenium and molybdenum which can stand high temperature environment were discussed. The Monte Carlo calculation results were compared. Sensitivity coefficients were calculated for main isotopes in the core, and finally the demand for evaluated nuclear data in space reactor area was pointed out.