Abstract: To analyze the characteristics of burnable poisons used in the micro gas-cooled reactor, this paper investigates how the kinds and layout of burnable poisons influence the reactor characteristics, such as reactivity and lifetime, based on the long-lifetime core (15 MW-20 a) model, short-lifetime core (5 MW-1 a) model and longer-lifetime core (5 MW-3−10 a) model, using Monte Carlo procedure. The results show that, as for the long-lifetime core, the monolithic type Er₂O₃ can reduce the core excess reactivity effectively with a certain reactivity punishment at the end of lifetime, and the monolithic B₄C can reduce the core excess reactivity excellently with a better power distribution if an inhomogeneous distribution layout of B₄C is applied, and the separated type B₄C makes the characteristic curve of burn-up flatter. As for the short-lifetime core, the separated type Gd₂O₃ is an appropriate choice while the B₄C with usual layouts is not, but it has a good behavior if the B₄C disperses in the core graphite as the burnable poison. As for the longer-lifetime core, the separated type Gd₂O₃ not only can control the core excess reactivity effectively, but also can guarantee the core have the inherent safety of automatic shutdown only by the negative temperature feedback. These results will instruct the follow-up development of micro gas-cooled reactor devices.