Abstract: The depth of floor failure zone is a key parameter in the design of mine floor water hazard prevention and water inrush risk assessment. Due to the difficulty of deep exploration work, the measured data of deep floor failure zone depth is extremely scarce, which brings great difficulties to the floor water control work of deep mining. By means of downhole borehole water pressure test and borehole imaging test, the depth of floor failure zone was measured on the complete area and broken area of the floor in the deep working face of Linxi Mine respectively. Numerical simulation method is used to study and analyze the development law of floor failure depth under the condition of faulted and non-faulted floor.. The research results show that: under the condition of no faults in the floor, the development of floor failure depth has experienced the evolution law of "increase-stability" with the advancement of the working face; Under the condition that the floor has faults, the development of the failure depth of the floor has experienced the evolution law of "growth-stable-sudden-increase-stable" with the advancement of the working face; The development of faults in the floor will deepen the depth of floor failure zone; The actual measurement determines that the depth of the failure zone in the complete area of the bottom floor of the deep working face is about 23.58m, and the depth of the failure zone in the fractured area of the fault is about 37.45m. The research results will have important reference value for most mines facing deep mining water hazards.