With the deepening reform of China's energy structure, actively developing nuclear energy has become a major trend. The fourth-generation nuclear energy system represents the trend and technological frontier of nuclear power development, therefore, the research on lead-cooled fast neutron reactors has attracted much attention internationally. Based on the open-source software OpenMC developed by the Massachusetts Institute of Technology(MIT) for the Monte Carlo neutron transport equation in reactors, the advanced lead fast reactor European demonstrator (ALFRED) was selected as the research object, and two distinct coolant materials were used to conduct physical calculations of the lead cooled fast reactor core. The results show that under identical fuel loading conditions, the utilization of lead-bismuth coolant yields a significant enhancement in the reactor core's initial reactivity by 271 × 10^-5. Moreover, the reactor core manifests a heightened proportion of effective delayed neutrons during normal commercial operation. Additionally, the neutron spectrum of the reactor core exhibits broader and harder characteristics, while also showcasing improved burning efficacy for the ²³⁹Pu nuclide within the fuel matrix. Consequently, the employment of lead-bismuth alloy coolant within the ALFRED reactor core culminates in a heightened effective multiplication factor. This augmentation holds promise for enhancing the controllability and burnup performance of the reactor core, while concurrently mitigating the generation of radioactive waste. The research results furnish valuable insights into the design and performance optimization of the reactor core for the lead-cooled fast neutron reactor European demonstrator.