Abstract: The nuclear rocket engine has large power, long life and high specific impulse, so it has an irreplaceable advantage in the implementation of deep space exploration and interplanetary missions. The miniaturization is an important development trend of nuclear rocket engine. Based on this, a small nuclear rocket engine reactor core scheme with tungsten-based CERMET fuel (CERMET-SNRE) was proposed. The Monte Carlo code (MCNP) was used to accurately model and calculate the relevant physical parameters. The results of calculation and analysis show that the reactor core of CERMET-SNRE has hard neutron energy spectrum, low burnup, enough excess reactivity, reasonable power distribution, and sufficient worth of control drum and safety rod. Under launch dropping accident, the effective neutron multiplication factor is less than 0.98. The reactor core scheme is reasonable and satisfies design requirements.