Abstract: In order to study the application of thorium uranium fuel in the CANDU6 reactor, the code DRAGON/DONJON is adopted to study the time-averaged equilibrium core of CANDU 6 with37-element bundle assembly of discrete thorium uranium fuel rods. The results show that, when the assembly is the uranium rods with 2.5% enrichment of ²³⁵U and the 37-element bundle assembly of thorium rods arranged in the 1, 2 and 3 layers, and under the refueling scheme of 8 bundles with 3 burnup partition, the coolant void reactivity of the assembly is lower than that of the 37-element bundle assembly (NU-37 assembly) with natural uranium and the assemblies containing mixed thorium uranium pins; that the max time-averaged channel/bundle power of the core respects the limits (less than 6700 kW/860 kW); that the fuel conversion ratio is higher than the CANDU6 reactor with natural uranium; and that the discharge burnup is up to 13400 MW·d/t(U). Therefore, the 37-element bundle using discrete thorium uranium fuel is applicable in the CANDU6 reactor, without major modification of the structure of the core and operation modes, and the design of fuel assembly and core provides a reference for the thorium uranium fuel in CANDU6.