Abstract: Under reactor accident conditions, the gas-liquid two-phase flow in the rod bundle channel exhibits complex multidimensional transient characteristics. The kinetic behaviour of bubbles, such as agglomeration, fragmentation and migration, will lead to drastic fluctuations in the interphase distribution and phase interface in gas-liquid two-phase flow. Therefore, the accurate measurement of two-phase flow parameters in the rod bundle channel is crucial for reactor design optimization. As a flow imaging technique based on the conductivity method, the wire-mesh sensor (WMS), which mainly includes the wire-mesh measurement module and the signal processing and acquisition circuit module, has extremely high temporal and spatial resolution and is capable of collecting the full flow field information of gas-liquid two-phase flow in different channel cross-sections with high spatial and temporal resolution. In this paper, the complexity of the gas-liquid flow behaviour in the prototype 5×5 rod bundle channel was focused, and COMSOL software was used to numerically simulate and analyse the measurement accuracy of the WMS, the bubble size within a reasonable intervalwas set, the relative error of the WMS measurements on the share of different vacuoles was considered, and the key parameters such as electrode filament diameter, transverse spacing, and longitudinal spacing were systematically adjusted, to analyze the relative errors of WMS measurements under different vacuole shares. By simulating the distribution of the potential field under different conditions, the influence of these factors on the measurement accuracy of the WMS technique in complex flow fields is explored to provide a theoretical basis for the design and optimization of the subsequent WMS that should be used for the study of the two-phase flow characteristics in the 5×5 rod bundle channel. In the electric field simulation process, intermittent overshooting phenomenon will be produced, resulting in the post-processing of the electrical signal data, the emergence of the share of negative air bubbles does not meet the actual physical phenomena, the research process of its truncation processing for correction effectively improves the clarity of the identification of bubbles. In addition, an embedded WMS prototype suitable for a 5×5 rod bundle channel was fabricated during the study, and the reliability of the numerical simulation results was verified by gas-liquid two-phase stratification experiments. Combined with the experimental and simulation results, the design with electrode wire diameter of 0.1 mm, lateral spacing of 2 mm and longitudinal spacing of 2 mm can effectively improve the measurement accuracy under the comprehensive consideration of the spatial resolution and crosstalk effect of the WMS.