Abstract: Abstract: In order to study the development law of overburden failure height under repeated mining in multiple coal seams, taking the mining of No. 3 coal seam in Gongwusu coal mine as the engineering background, the height of overburden water conducting fracture zone during single-layer mining and repeated mining is obtained through field measurement and numerical simulation. 3DEC numerical simulation studies the failure characteristics of overburden under single coal seam mining and repeated mining, The fracture development mechanism of overlying rock under repeated mining and the calculation method of fracture zone height are analyzed theoretically. The results show that the combination of borehole flushing fluid observation and borehole peeping is more accurate. Under the condition of repeated mining of Gongwusu 16 coal, the split mining ratio is 15.14 and the collapse mining ratio is 3.15; The simulation shows that the fractures on both sides of the goaf are obviously developed and discrete, the middle fracture is closed, and the fracture height is close to the measured value; Three kinds of calculation methods for the development height of repeated mining fracture zone are put forward, which provides a theoretical basis for determining the development height of overlying rock fracture under the condition of repeated mining.