In this study, the effective multiplication factor Keff, neutron energy spectrum, radial power peaking factor distribution, temperature reactivity, and reactivity control under different fuel lattice element ratios from the perspective of neutron physics using Monte Carlo method were carried out. At the same time, continuous feeding was used to meet the critical requirements of core burn up calculation. Finally, an additional breeding layer was set in the absorption and reflection layers outside the core to study the breeding characteristics of the breeding layer. The calculation results show that the physical properties of the core are better when the fuel lattice element volume fraction is small between 20 and 30%. Due to the thermal conductivity of the fuel, the hot spot of the radial power density is mainly concentrated at the center of the core. Additionally, thorium-based molten salt has a good temperature reactivity, diverse control modes and better safety. By setting the breeding layer in the absorption layer with a softer energy spectrum, it has a better fuel value ratio. The relevant calculation in this study has a certain reference significance for the research of molten salt reactor and thorium-based fuel cycle in the future.