Abstract: Thorium is a fertile material and is converted into ²³³U in nuclear reactors, which could greatly improve existing reserves of nuclear fuel resources. In order to use thorium, block-type modular high temperature gas-cooled reactor GT-MHR was studied, and low-enriched uranium, weapon-grade plutonium and reactor-grade plutonium were chosen as the driver fuels for the thoriumbased GT-MHR. The lattice transport code DRAGON was used to analyze the characteristics of the prismatic fuel block, including the neutron energy spectrum at beginning of life, infinite multiplication factor, fuel burnup, conversion ratio, and the mass of ²³³U and ²³²Th. The analysis shows that when the mass fraction of the initial fissile material is close to 9%, compared with the low-enriched uranium and weapon-grade plutonium, the reactor-grade plutonium has the hardest neutron energy spectrum at beginning of life and high conversion ratio, and reaches a burnup of 90 GW•d/tHM, and achieves the minimum reactivity swing during the fuel cycle. Moreover, the ratio of remaining ²³³U to the consumption of ²³²Th reaches 0.566 at a burnup of 75 GW•d/tHM.