Inherently poorer moderation in supercritical water-cooled reactors (SCWRs) due to average density lower than in light water reactors and the resulted spectral shift can be useful when we apply thorium fuel-cycle instead of uranium–plutonium one, according to an ongoing study in Budapest University of Technology and Economics (BME) Institute of Nuclear Techniques (NTI). Upon this conclusion, a thorium-fueled SCWR design (Th-SCWR) has been proposed by BME NTI. In the current feasibility study phase, detailed three-dimensional (3D) computational fluid dynamics (CFD) calculations with novel neutronics analysis were coupled and conducted separately. Neutronics calculations provided the distribution of heat source, while the CFD analysis gave back axial distribution of coolant density (this iteration was repeated until an acceptable convergence). This paper presents the CFD analysis on thermal hydraulics of the initial design (two CFD models without any spacer device and one model with wrapped wire spacer) of Th-SCWR fuel assembly. As results of the preliminary design of Th-SCWR cladding wall, coolant and fuel temperatures have been determined; the flow field with and without spacer device has been showed, and the application of wrapped wire spacer has been proposed.