Abstract: The heat pipe cooled reactor featured with small volume, high power density, long lifetime and high adaptability to environment, has promising applications for space exploration and underwater vehicles. Thus there is great significance of conducting reactor design and analysis. Based on a series of literature reviews, a 2.4 MWth lithium heat pipe cooled reactor core with long lifetime and low level noise was designed. Monte Carlo program MCNP was used for calculating the power distribution, reactivity feedback and critical safety characteristics of the reactor core. A code MCORE coupling MCNP5 and ORIGEN2 was used for calculating the core lifetime. The results show that the peak power factor is 1.42, the core lifetime is 14 a, and core parameters satisfy the requirements, which provide reference to the design and application of the micro nuclear power source.