Abstract: To investigate the multi-scale thermodynamic and dynamic characteristics of supercell hailstorm over the mountainous regions of Guizhou and its interaction with the topographic environment, this study integrates Weather Research and Forecasting (WRF) simulations with radar observations and the fifth-generation ECMWF reanalysis v5 outputs to validate the “channel-zero domain” hail formation theory. Synoptic analysis reveals that the Guiyang supercell hailstorm of April 4, 2012, was synergistically triggered by 500 hPa upper-level trough, 700 hPa shear line, 850 hPa cyclone, “upper-dry-lower-moist” stratification and orographic lifting. Radar observations indicate that the supercell persisted for 3 h, exhibiting composite reflectivity of up to 65 dBZ, an 11 km echo top height, and mesocyclone/bow echo signatures. The pivotal dynamic structure is characterized by the vertical development axis of the mesocyclone supporting and maintaining a velocity “zero-domain” channel that penetrates the hail cloud. This channel facilitates the rapid transport of water vapor and energy, allowing the maximum reflectivity core to remain stably positioned within the −10°C–0°C supercooled water layer Thermodynamic–dynamic diagnostics indicated that a 24 m s⁻¹ vertical wind shear induced mesocyclogenesis, strong updrafts from 900 to 200 hPa provide dynamic support, and high humidity in the mid-to-low levels establishes unstable stratification. The “positive upper–negative lower” potential vorticity (PV) structure, together with moisture and thermal helicity, shows distinct indicative significance at different stages: variations in PV and thermal helicity herald initiation during the developing stage; enhanced helicity and vertical extension of the PV column mark the mature stage; and decay of helicity signals system collapse during the dissipation stage. WRF cloud microphysics simulations reproduce the processes of cloud droplet collision-coalescence, ice crystal generation, and graupel dry growth. During the hail-fall stage, particles undergo multiple cycles of sedimentation and wet growth in the front-to-middle part of the “channel-zero domain” eventually forming large hailstones at the rear of the storm cloud. These results further validate the “channel-zero domain” theory by elucidating the coupled dynamic-microphysical mechanism in which the mesocyclone vertically supports the zero-domain channel, sustaining the hailstorm over complex terrain.