To study the movement law of overlying strata in gently inclined coal seam mining under deep buried conditions, No.140504 Face of Kouzidong Mine was taken as the background, 3DEC numerical simulation was used to study the movement law of overlying strata in the goaf of 1000m deep mine. It was found that the vertical displacement of the gently inclined coal seam was asymmetrically distributed along the center of the goaf, and when the dip angle was 8°, the dip angle had little effect on the subsidence of the strata above 400 m in the uphill and downhill parts. With the advancement of the working face, the horizontal displacement of the overburden rock had both positive and negative values, indicating that the rock layer at this depth would collapse. At this time, the horizontal displacement and vertical displacement of the layer would increase rapidly. Based on the key layer theory, the height of the caving zone was calculated and the accuracy of the numerical simulation was verified.