Recently, deep coal mining has posed a significant challenge owing to the threat of water inrush from highly pressured aquifers in the floor strata. Water inrush in the floor strata is often associated with the structural characteristics of the underlying fault zones. The permeability of these fault zones is a critical factor in determining their potential as conduits for water flow. The variation in permeability is attributed to the varying cementation degree across different locations within the fault zones. Hence, this study is based on the key stratum theory and introduces the concept of a water-blocking key stratum within fault zones. This research focuses on the engineering context of the 16th coal seam above the lower coal seam in the 10603 working face of the Yangcun Coal Mine's tenth mining area. The study investigates the activation characteristics of the 10605F5 reverse fault zone, which cuts through the working face. Various methods, including test of simulation of similar materials and numerical simulations, are employed to analyse the hydraulic pressure distribution and the impact of mining activities on the water-blocking key stratum within the 10605F5 reverse fault zone. The research findings will provide valuable insights for preventing fault activation and water inrush.