Abstract: Magnetic Resonance Velocimetry (MRV) is becoming a crucial experimental technology for flow field visualization, flow heat transfer mechanism investigating, and numerical model validation. In recent years, the MRV technology has been employed in experimental investigations of coolant channel flow fields in nuclear reactor core fuel assemblies, providing fundamental data for core thermal hydraulic characteristics research and safety analysis. A literature overview of the research progress using MRV technology in experimental studies on the flow field of reactor core fuel assembly channels is presented in this paper. The three-dimensional coolant flow field within a 2 × 2 simplified rod bundle channel was measured using MRV, and quantitative comparisons were conducted with PIV measurement results from previous literature to investigate the key parameters influencing the measurement accuracy of MRV. In this study, MRV tests were performed under two conditions of Re = 12500 and 25000, respectively. The results indicate that the axial velocity from MRV within the investigated channel has a maximum discrepancy of 5.05% compared to the PIV data reported in the literature.